A hitherto unknown and important benefit of E10

[Chris Garner]

Bob,
Water entering the cylinders causes carbon to disappear??
Not in my case after trying to get a Supalloy head to seal - hate the things, made out of milk bottle tops!
Not having the equipment to correct the distortion, I reverted back to a CI, H/C head. Problem solved.

[Ruairidh Dunford]

50 + years ago, when I and friends were doing 15 to 20 thousand miles a year, I can't remember ever doing a "decoke". Depending upon the road mileage between events, I did give the valves a light grind before any competition use - but never bothered scraping off carbon. Perhaps by the 1960s and 1970s oils and piston materials (that combined to reduce wear and blowby) had improved so much that the old decoke routine was no longer necessary. Do high-mileage owners of today find the same thing?

In over 250000 miles of Austin Seven driving since 1990 I have never, ever, done a decoke.

[Ivor Hawkins]

Like Tony and Ruairidh, I’ve driven many thousands of Vintage Austin miles and only decoked the motor because that was the recommendation...I suppose that was a complete waste of time then!

[Colin Morgan]

I run a 3-bearing engine that has not been apart in decades and was left idle between 1975 and 1999. I de-coked it twelve years ago after ten years running, partly because I could see carbon build-up down the plug holes and also because this was recommended in the literature. There was about half a mm of black to scrape off. I don't remember it making any difference to the running.

So, do engines that haven't been decoked reach sensible equilibrium where no more carbon builds up, or are they these engines in such good condition that carbon hardly builds up at all and they remain 'clean'?

If E10 works to remove carbon that is present somehow, those running on E10 will see a cleaner engine than before? I am using the locally alcohol free (so far as I know) BP Ultimate and so - if there is such an effect - I haven't seen it.

[David Stepney]

The only time I have decoked an engine is when it has been apart to deal with some other problem such as a burned valve. I suspect the advice about decoking an engine was because usually one ground the valves in as well.

[Duncan Grimmond]

My Toyota camper van seems to have lost some of its mpg since I've been using E10 but that may be my imagination or a slightly heavier right foot. I do try to run it on an economy setting throttle but being an automatic it's difficult to maintain consistency.
Cleveland Discol was certainly sold on the "cleaner burning, lower oil consumption" ticket. A quick look at 1960s advertisements shows people were convinced (or paid to be so) and Practical Motorist was still giving advice on the kerbside de-coke at the time.

[andrew34ruby]

It has always seemed to me that every engine I have dismantled had about the same amount of carbon, so presumably the carbon does not gradually build up over time.

And yes I have noticed that any engine that has had a slightly leaking head gasket, leaking water into a cylinder over some time, has zero carbon in that cylinder.

I use E10 in the seven, and yes it seems to be using a bit less oil, but that is an impression, not a scientific fact.

[Bob Culver]

Because ethanol has markedly reduced calorific value fuel consumption should increase. Cars running on all alcohol were jetted for much increased mixture. Ethanol fuel should be sold at a discount

[Ivor Hawkins]

Because ethanol has markedly reduced calorific value fuel consumption should increase. Cars running on all alcohol were jetted for much increased mixture. Ethanol fuel should be sold at a discount

Now that’s a post we can all understand and agree with Bob!

[David Stepney]

Returning to the thread's original point, and taking up Andrew's thought, I too have been using E10 happily in the RP since it was first introduced and have seen no discernible difference in either fuel or oil consumption Both remain at 36 mpg messing and 250 mpp respectively. In the case of the oil consumption I wipe most of that off the nearside crankcase. I suspect that, like many Austin Seven engines, mine leaks more that it burns.