Flexfuel Engine Cleaning? Scam?

Flatulentoldgoat

A local business is offering some sort of fantastic carbon engine cleaning service that apparently gives you a 15% boost in MPG.

Is this some kind of snake oil or what?

Apparently Hybrid petrol and diesel benefits from it and they have some sort of machine that gives the engine a deep carbon cleaning.

tacpot12

Cleaning the engine of carbon can produce improvements in MPG, but 15% sounds a bit too good to be true. Cleaning can only produce a significant improvement if the engine has a significant amount of carbon buildup. If you don't know you have this problem, I wouldn't invest in an engine clean, and if I did have the  problem I would not use someone that advertised the  service without thoroughly checking them out.

I have recently tried a fuel injector cleaner in my petrol car. It cost £4.99 for the bottle of cleaner from a local motor factor, and did improve fuel economy by about 1.5 mpg (about 5%), but unexpectedly it also removed the slight hesitancy that occurred when you first pressed the throttle pedal - I thought the throttle butterfly was sticking, but it must have been the injectors being slightly clogged. If this treatment can produce a 5% improvement, then it is perhaps not unreasonable that a fill de-coke would produce a 15% improvement, but only if the engine is really bad. 

You could always ask them what improvement they will guarantee on your car, and see what they say. I expect they will say that there are too many variables to be able to guarantee an particular level of improvement, which basically means they want you to invest £xxx on the off-chance it improves the performance by a measurable amount. I was prepared to spend £4.99 on the off-change, I'm not sure I would be prepared to spend more... 

AdrianC

Some engines have direct fuel injection, where the fuel is injected into the combustion chamber, not into the intake manifold and ports. Combined with crankcase breather fumes and EGR, it's possible for the intake ports and valves to get a build-up of residue.

Cleaning can, theoretically, remove that.

I suspect, however, that once there's any substantial build-up, it's going to take a strip-down and mechanical cleaning, not just a bit of goop sprayed up the inlet tract, in order to make any real difference.

If the build-up is so bad that economy has suffered by 15%, then the driver would definitely notice a substantial performance loss.