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    • reeac
    • By reeac 13th Oct 16, 5:36 PM
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    reeac
    Effect of oil viscosity on mpg.
    • #1
    • 13th Oct 16, 5:36 PM
    Effect of oil viscosity on mpg. 13th Oct 16 at 5:36 PM
    Took my 11 year old Jazz back to the agents for service and mot recently and noticed that they had used 0w20 engine oil instead of the usual 5w30. Since then it's been displaying a bit over 57 mpg. as opposed to its normal 53 mpg. Early days maybe as it's only 200 miles so fat but I'm beginning to think that it's a genuine 8 percent increase as I've never seen 57 mpg for more than a few miles before and I've had the car since new. Time will tell but has anyone else seen such an effect? The oil cost was no more than for the 5w30 supplied by my local garage last time around so looks like a win/win.
Page 1
    • Mr.Generous
    • By Mr.Generous 13th Oct 16, 5:43 PM
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    Mr.Generous
    • #2
    • 13th Oct 16, 5:43 PM
    • #2
    • 13th Oct 16, 5:43 PM
    the 0 part is good, it means the oil runs like water when cold for better protection at start up. The down side is the 20 means it never really behaves like a thick oil and clings when its hot.
    Better MPG at the risk of engine wear on longer trips. If its a short journey low mileage car I would be willing to risk it with regular oil changes, what do Honda advise?
    The wider the band on a multigrade oil generally the better. A 0-w30 or 40 might be better, mobil1 0-w40 fully synthetic for my car while other family cars are 5-w30's IIRC.
    • reeac
    • By reeac 13th Oct 16, 7:12 PM
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    reeac
    • #3
    • 13th Oct 16, 7:12 PM
    • #3
    • 13th Oct 16, 7:12 PM
    It was the Honda agent who did it. I mentioned it when I read through the invoice but the chap at the desk made no comment. Anyway, looking on the Internet I see that 0w20 is all the rage now for many different car models. I've no concerns regarding engine protection particularly as the car is mostly used for local running around but I'm surprised at the magnitude of the fuel saving. As I said, I'll be watching the fuel computer to see if it's a real effect.
    • Strider590
    • By Strider590 13th Oct 16, 9:34 PM
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    Strider590
    • #4
    • 13th Oct 16, 9:34 PM
    • #4
    • 13th Oct 16, 9:34 PM
    It was the Honda agent who did it. I mentioned it when I read through the invoice but the chap at the desk made no comment. Anyway, looking on the Internet I see that 0w20 is all the rage now for many different car models. I've no concerns regarding engine protection particularly as the car is mostly used for local running around but I'm surprised at the magnitude of the fuel saving. As I said, I'll be watching the fuel computer to see if it's a real effect.
    Originally posted by reeac
    I'm calling BS on this one, air filter would have a much greater effect on MPG.
    If the old oil was really old and contaminated (low mileage, long service gaps), you could get a lot of oil vapour being directed back into the inlet manifold via the PCV, burning oil vapour can make a car as much as 5% less efficient.

    Running the wrong oil in an engine can have very detrimental effects, the advertising for 0w5 engine oils in the 80's and 90's, caused sooooo much damage to cars with hydraulic lifters (most Fords of that time).

    Engines need oil to flow at a certain viscosity, too high and it's not reaching parts fast enough to protect them (particularly the bottom end), too low and it's flowing like water, the pump can't maintain pressure and you get the same effect.

    When was it last serviced?
    Last edited by Strider590; 13-10-2016 at 9:44 PM.
    Having the last word isn't the same as being right.......

    "Never confuse education with intelligence"
    • reeac
    • By reeac 13th Oct 16, 10:18 PM
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    reeac
    • #5
    • 13th Oct 16, 10:18 PM
    • #5
    • 13th Oct 16, 10:18 PM
    Strider: The car was serviced in September 2015 and had covered just under 5000 miles since. As the air filter and plugs were changed then they were not touched in September 2016.
    I appreciate that you're an all round expert but in this case your predictions are wrong. It happens also that apart from having a Cambridge PhD in physics I also spent some time in the Shell Thornton Research Labs. so I know about oils.
    • forgotmyname
    • By forgotmyname 13th Oct 16, 10:39 PM
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    forgotmyname
    • #6
    • 13th Oct 16, 10:39 PM
    • #6
    • 13th Oct 16, 10:39 PM
    Car runs better straight after a service (shock), but you have only done 200 mile so not really a proper test.

    How does the friction compare between a 0 and a 5 oil?
    Punctuation, Spelling and Grammar will be used sparingly. Due to rising costs of inflation.

    My contribution to MSE. Other contributions will only be used if they cost me nothing.

    Due to me being a tight git.
    • Strider590
    • By Strider590 13th Oct 16, 11:01 PM
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    Strider590
    • #7
    • 13th Oct 16, 11:01 PM
    • #7
    • 13th Oct 16, 11:01 PM
    Strider: The car was serviced in September 2015 and had covered just under 5000 miles since. As the air filter and plugs were changed then they were not touched in September 2016.
    I appreciate that you're an all round expert but in this case your predictions are wrong. It happens also that apart from having a Cambridge PhD in physics I also spent some time in the Shell Thornton Research Labs. so I know about oils.
    Originally posted by reeac

    I know of far too many qualified idiots who scraped through uni by memorising text books and cheating from their peers, I know one young lady in particular who is one of the most clueless engineers i've ever met, now earns a lot of money working for BP as part of their drive to promote women in engineering, not sure exactly what she does, but it's probably not much.
    So when someone throws their academic qualifications in my face, I can tell you it means less than nothing to me.

    I myself have a theoretical degree in the theoretical physics.
    Last edited by Strider590; 13-10-2016 at 11:06 PM.
    Having the last word isn't the same as being right.......

    "Never confuse education with intelligence"
    • BeenThroughItAll
    • By BeenThroughItAll 14th Oct 16, 7:31 AM
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    BeenThroughItAll
    • #8
    • 14th Oct 16, 7:31 AM
    • #8
    • 14th Oct 16, 7:31 AM
    I know of far too many qualified idiots who scraped through uni by memorising text books and cheating from their peers, I know one young lady in particular who is one of the most clueless engineers i've ever met, now earns a lot of money working for BP as part of their drive to promote women in engineering, not sure exactly what she does, but it's probably not much.
    So when someone throws their academic qualifications in my face, I can tell you it means less than nothing to me.

    I myself have a theoretical degree in the theoretical physics.
    Originally posted by Strider590
    Goes to show how much of an expert you are if you're comparing scraping through memorising text books with a PhD. You know it's not a multiple choice then have a doctorate, right?

    Plus, for every 'qualified idiot' there are ten unqualified idiots.
    • reeac
    • By reeac 14th Oct 16, 8:49 AM
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    reeac
    • #9
    • 14th Oct 16, 8:49 AM
    • #9
    • 14th Oct 16, 8:49 AM
    [QUOTE=Strider590;71450252]
    So when someone throws their academic qualifications in my face, I can tell you it means less than nothing to me..[/QUOTE

    Must happen to you frequently given your attitude that everyone you encounter is an incompetent idiot.
    • Strider590
    • By Strider590 14th Oct 16, 10:56 AM
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    Strider590
    Must happen to you frequently given your attitude that everyone you encounter is an incompetent idiot.
    Originally posted by reeac
    I give everyone a chance to prove they're not an idiot, I think that's a fair way to do things...... I can't help it if a lot of people blow that chance.

    That said I never specifically called you an idiot, i was merely pointing out that throwing academics around is entirely meaningless.

    When you come on here claiming that lower viscosity engine oil gave you miraculously better MPG, your lying to not only yourself, but to other people AND to make it worse your recommending something that could damage their vehicles.

    I mean it sounds like you went to a main dealer (agents?), nobody who knows cars would do that, you'd be lucky if they'd even changed your oil at all, let alone actually driven it into the service bay. They're underpaid trainee technicians, who have unrealistic work targets to meet and WILL take shortcuts.

    It could even be they carried out a firmware mod on the ECU while it was there and altered the cars ignition timings, this happens A LOT at main dealers, they covertly fix issues that the manufacturer has identified so that these issues never become public recalls.

    Whatever the reason, it's not the oil. You don't know the specified pressure or flow rate for that engines oil galleries and as I explained, the wrong oil can and often does cause premature engine wear. The manufacturer has spent millions of £ on teams of very highly qualified and experienced engineers, determining the correct engine oil for that vehicle.

    The engine in my kitcar runs 20w50 racing spec mineral oil, before I had the engine rebuilt, it ran 0w30 fully synth. The man that rebuilt my engine was an ex British Leyland engine designer, motorsport engineer and co-founder of Aldon Automotive, when he spoke, I listened.
    Having the last word isn't the same as being right.......

    "Never confuse education with intelligence"
    • missile
    • By missile 14th Oct 16, 2:37 PM
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    • 3,956 Thanks
    missile
    Changing from 5W30 to 0W20 will obviously reduce friction, that is a no brainer. However, I also find it very hard to believe it would make 8% difference to fuel consumption.
    Sure it will make a small improvement but I would suggest OP is exaggerating the benefit just like these miraculous claims of improved mpg, oil companies make for premium grade fuel.
    "A nation's greatness is measured by how it treats its weakest members." ~ Mahatma Gandhi
    Ride hard or stay home
    • harrys dad
    • By harrys dad 14th Oct 16, 4:24 PM
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    harrys dad
    You are still paying main agent prices to service your 11 year old car? That is a serious waste of money.
    • jimjames
    • By jimjames 14th Oct 16, 5:14 PM
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    jimjames
    Sure it will make a small improvement but I would suggest OP is exaggerating the benefit just like these miraculous claims of improved mpg, oil companies make for premium grade fuel.
    Originally posted by missile
    If it really was that easy wouldn't all the manufacturers being doing that? Might have saved VW a bit of reputational damage if they'd actually reduced emissions!
    Remember the saying: if it looks too good to be true it almost certainly is.
    • Joe Horner
    • By Joe Horner 14th Oct 16, 5:24 PM
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    Joe Horner
    Changing from 5W30 to 0W20 will obviously reduce friction, that is a no brainer. However, I also find it very hard to believe it would make 8% difference to fuel consumption.
    Originally posted by missile
    8% does seem quite high but people often don't realise how much of the energy in a tank of fuel is wasted inside the engine compared to what's used to drive the wheels.

    In typical town driving something like 2/3 of every litre is used JUST to keep the engine running and less than a coke can's worth goes to actually turning the wheels / moving the car. So increases in engine efficiency do have an apparently disproportionate effect on fuel consumption.
    • forgotmyname
    • By forgotmyname 14th Oct 16, 5:50 PM
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    forgotmyname
    Maybe they checked the tyre pressures and put some extra air in?
    Punctuation, Spelling and Grammar will be used sparingly. Due to rising costs of inflation.

    My contribution to MSE. Other contributions will only be used if they cost me nothing.

    Due to me being a tight git.
    • reeac
    • By reeac 14th Oct 16, 5:53 PM
    • 955 Posts
    • 385 Thanks
    reeac
    I give everyone a chance to prove they're not an idiot, I think that's a fair way to do things...... I can't help it if a lot of people blow that chance.

    That said I never specifically called you an idiot, i was merely pointing out that throwing academics around is entirely meaningless.

    When you come on here claiming that lower viscosity engine oil gave you miraculously better MPG, your lying to not only yourself, but to other people AND to make it worse your recommending something that could damage their vehicles.

    I mean it sounds like you went to a main dealer (agents?), nobody who knows cars would do that, you'd be lucky if they'd even changed your oil at all, let alone actually driven it into the service bay. They're underpaid trainee technicians, who have unrealistic work targets to meet and WILL take shortcuts.

    It could even be they carried out a firmware mod on the ECU while it was there and altered the cars ignition timings, this happens A LOT at main dealers, they covertly fix issues that the manufacturer has identified so that these issues never become public recalls.

    Whatever the reason, it's not the oil. You don't know the specified pressure or flow rate for that engines oil galleries and as I explained, the wrong oil can and often does cause premature engine wear. The manufacturer has spent millions of £ on teams of very highly qualified and experienced engineers, determining the correct engine oil for that vehicle.

    The engine in my kitcar runs 20w50 racing spec mineral oil, before I had the engine rebuilt, it ran 0w30 fully synth. The man that rebuilt my engine was an ex British Leyland engine designer, motorsport engineer and co-founder of Aldon Automotive, when he spoke, I listened.
    Originally posted by Strider590
    Oh dear, yes I took the Honda to the main dealer! I do that every 3 years or so mainly so that I can borrow a courtesy car for the day and see whether the latest Jazz is any improvement on mine. The verdict so far has been negative. That's called "spend to save" (it costs me £10 for insurance but saves many £k on trading up). Other years I use a local garage which, in fact, isn't noticeably cheaper but is 2 miles away as opposed to 20.
    Even worse, my xj8 goes to the main Jag. dealer once a year and has done so for 14 years now so they can't be treating it that badly as it's still running well. Costs little more than the Honda ...l'm wondering if they give a discount for elderly Jags. as a PR gambit.
    Regarding engine damage I belatedly looked in my Jazz manual and see that you can use anything from 0w20 up to 5w40 over the temperature range below -30 up to above 40C so no probs. with the thin oil. I assume that you would trust Honda design engineers as much as you would your ex BL man.
    The car is still showing 57.5 mpg but, as I said initially, I'm waiting to see if it's true effect. I wouldn't have posted this info. if I hadn't found it surprising. Hoping to get useful solid info. from others but no luck so far. Maybe I should try a different forum..... .
    • takman
    • By takman 14th Oct 16, 7:00 PM
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    takman
    Car runs better straight after a service (shock), but you have only done 200 mile so not really a proper test.

    How does the friction compare between a 0 and a 5 oil?
    Originally posted by forgotmyname
    Actually that should be a shock. If a service makes the car run better then that means it's not being serviced often enough. A service should maintain the cars performance and not really improve it because the performance shouldn't noticeably degrade between services.

    To the OP over how many miles is the 53MPG average and have you done the same trips when you were getting 57MPG?. My car sometimes varies more than 4 MPG between tankfuls depending on the weather and the type of trips I am doing.
    • reeac
    • By reeac 14th Oct 16, 8:03 PM
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    • 385 Thanks
    reeac
    I've had the car from new so 11 years and it's done just under 55,000 miles. I reset the fuel computer from time to time but not in any consistent manner but it normally reads between 52 and about 53.5 mpg. Since the service it has never dropped below 57.0 but that's only around 200 miles so far. I can't guarantee to do exactly the same journeys as in the past but I'm trying to drive in the same manner as usual. As long as the figure stays at or above 57.0 then I think that I'm onto something as it has never read that before more than momentarily.
    • gabitzul
    • By gabitzul 17th Oct 16, 12:13 PM
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    gabitzul
    Don't have anything to add to the fuel consumption debate, but in my 10 reg Jazz (1.4 manual) I have found that the computer is a bit over optimistic (usally shows 52-53 MPG). A brim to brim test showed about 50 MPG.

    Still, very good and I am happy with it, so much so that I prefer to use the Jazz when available (it's wife's car) instead of my Merc C Class as it's better in town and with very light controls.
    • mcpitman
    • By mcpitman 17th Oct 16, 1:13 PM
    • 396 Posts
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    mcpitman
    Strider: The car was serviced in September 2015 and had covered just under 5000 miles since. As the air filter and plugs were changed then they were not touched in September 2016.
    I appreciate that you're an all round expert but in this case your predictions are wrong. It happens also that apart from having a Cambridge PhD in physics I also spent some time in the Shell Thornton Research Labs. so I know about oils.
    Originally posted by reeac
    What on earth are you asking on here for then?

    Maybe they checked the tyre pressures and put some extra air in?
    Originally posted by forgotmyname
    Fair theory I was going to suggest.
    Life isn't about the number of breaths we take, but the moments that take our breath away. Like choking....
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