Engine oils, safe to mix ?

KaiserBill

Stoke wrote: »

Same grade of oil?

I think it`s 5W30 = but not too sure.

llllllllllllllllllllll

It doesnt matter if it is the same viscocity, the detergents in the fully synthetic oil will clean internal parts of the engine causing it to use/burn more oil, they also recommend that if you have a slight oil leak that Fully synthetic could make this worse because the detergent would clean the sludge that is holding back the leak and make it worse. (even have warning signs on the side of some oils)

I remember when mobil 1 bought our their fully synthetic oil, hot hatch owners thought it would give an increase of 10bhp when infact it caused all kinds of top end rattles and further problems because its ability to flow(viscocity) was to thick to lubricate on start up....this is where most engine damage is caused

If it was me on a 11 year old car with 75,000 miles on then increase the number before the W(Winter) or basically when cold
ie
5w30 is no good for older engines, its ability to flow on start up is just too thick go to 15w30 and use a mineral based oil not synthetic, cheap morrisons oil will be fine and save you money.

Iceweasel

llllllllllllllllllllll wrote: »

5w30 is no good for older engines, its ability to flow on start up is just too thick go to 15w30

I'm afraid this doesn't make any sense.

5w30 is less viscous at start-up than a 15w30.

londonTiger

Should point out synthetic and non synthetic are both the same base oils. Synthetic is just a marketing tag that stuck, synthetic is slightly filtered mineral oil that gas some if the unnecessary compounds removed and more of the beneficial compounds added. But after 3 or 4 months of driving there probably isn't much difference in the oil in the engine

AdrianC

llllllllllllllllllllll wrote: »

It doesnt matter if it is the same viscocity, the detergents in the fully synthetic oil will clean internal parts of the engine causing it to use/burn more oil, they also recommend that if you have a slight oil leak that Fully synthetic could make this worse because the detergent would clean the sludge that is holding back the leak and make it worse. (even have warning signs on the side of some oils)

ALL decent quality oils contain detergents. Synth, semi-synth, mineral. If a build-up of dirt is all that's holding the oil in from knackered seals, then you've got bigger issues than whether you put the right oil in.

It's quite simple.

The viscosity tells you how thick the oil is, cold and hot. It doesn't matter the base - a 15w30 is the same viscosity cold and hot whether it's synth, semi-synth or mineral.

The base gives you a rough indication of how long it'll last before starting to break down. That time will be shortened if extremes of heat are encountered.

Given the low price difference often encountered between good quality synth and semi-synth, and how difficult it is to find good quality minerals these days (other than a handful of specialist oils), I'll always go for synth if it's available in the right viscosity - especially in an air-cooled or turbocharged engine - but be happy to drop down to semi-synth otherwise or if the cost difference is large. Mineral would be a distress purchase.

There's umpteen good value specialist oil suppliers on the web - Opie are a good place to start. Petrol stations are usually extortionate.

londonTiger

whats better for your car.. 2 month old shell superdoopermax driven for 2000 miles. Or brand new supermarket brand engine oil?

Netwizard

londonTiger wrote: »

whats better for your car.. 2 month old shell superdoopermax driven for 2000 miles. Or brand new supermarket brand engine oil?

I'd go with the supermarket brand engine oil. At the end of the day, its likely to be made by one of the big oil companies anyway (Comma probably) so it will be just as good as any other!

I have run my cars on all sorts over the years (always the right grade however), and whether its Silkolene, Shell, Wilko, Asda or Lidl, I have never experienced any ill affects!

sabretoothtigger

Clean oil is best, thats the main thing. Theres no big drama from mixing oils but I would change it a bit sooner and that'll do more good then all the big claims made by the makers.

startled_cat

If it is a SAAB, I would be very careful doing anything not recommended for the car.Once bitten and all that.

AdrianC

londonTiger wrote: »

whats better for your car.. 2 month old shell superdoopermax driven for 2000 miles. Or brand new supermarket brand engine oil?

The Shell.

Decent oil lasts a LOT longer than 2mo/2k miles. Unless, of course, you're American...