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MG MGA - Super Unleaded

Having read Steve's comments re Super unleaded I have always used it on my MGA and according to Steve's MPG programme the A has averaged 32 mpg for the last 3 years, Consequently over the last few months I have been using super fuels( BP Ultimate or Shell V power) in my daily drivers one petrol and one diesel and the fuel economy has improved by 6-8% also I believe one has the added benefit of a cleaner combustion chamber and diesel turbo. Last week I had to fill up my Diesel BMW with ordinary diesel and the fuel consumption computer definitely showed 3-4 MPG less than usual- Not scientific but good enough for me
Paul
P D Camp

For some time I used Shell V Power in the "A" to get improved performance on my fairly high compression (flat top pistons) 1600 as the garage was closest to me. Over time, I found that the zinc alloy carbs and sender unit were getting very, very clean or even attacked and the brass floats were being got at too by the ethanol or something in the V Power. It also developed leaking jets (original type cork seals) and kindly stripped the paint off the chassis below in the process!
At the time I found on-line that V Power had 5% ethanol and that other high octane 'super' fuels didn't have ethanol yet. Once the the tank had been refilled a few times with BP Ultimate / local Tesco's Momentum the leakage stopped and the carb internals look like they used to...
I'm still using these two fuels, the car goes like stink and no problems as yet.
I know Barney's "A" is apparently impervious to ethanol!!! - but anybody else had these symptoms?
Happy Christmas everybody!
Pete
PeteT

I've been using the ordinary unleaded and getting at least 30 mpg. Engine is a bog standard 1500 with K&N filters and stub stacks. The spark plugs always look clean, the carb floats are a shiny brass colour and the cork seals have done at least 15,000 miles and don't leak. Our local petrol station is Jet, and that's where I fill up mainly. I am very happy with the way the car performs and have seen 90+ on the speedo (calibration checked by John Ostick) on more than one occasion. I have used super unleaded a couple of times but didn't notice any difference in performance, only a difference in price! I figure that any improvement in fuel consumption by using a 'super fuel' would outweighed by the cost over the standard unleaded.
Lindsay Sampford

There may be a more significant difference with engines that have an increased compression ratio?
Neil MG

I use super unleaded in my 1800, although I have filled with unleaded for comparison. The difference in performance 'seat of the pants' is very noticable and no pinking compared to unleaded with the same ignition advance (dynamically timed). Rubbish mpg (whichever fuel) of about 24, but hey, it's a sports car. Plenty of wellie with the right foot. I can afford the fun of the poor mpg just for the exhileration!

Like Lindsay, no sign of ethanol effects and that is fuel from whatever source that I happen to be close to when it's time to fill up.

Steve
Steve Gyles

Yes Neil, that's the thing. My 8.3:1 compression ratio is not going to benefit much from a 'higher octane' fuel, if that is what 'super unleaded is. Out of curiosity, what is the standard compression ratio for the 'B engine?
Lindsay Sampford

Higher ratio and obviously higher octane required..that is why they exist! I also consider that there is the extra complication of any additives added by the Shell, BPs etc of the world compared to the bottom feeding independents or similar who take it from any where and certainly don't add anything.
Neil Ferguson

Further to my original post my MGA is a Mk2 1622 cc coupe with ford 5 speed gearbox and according to the Engine rebuild invoice (supplied by the previous owner/restorer)has a higher lift cam and improved compression -skimmed head i.e. registers 170-175 on a compression tester I also have K&N filters and stub stacks and 123 ignition with sports coil I have seen the ton on the speedo confirmed by the revs and tend to drive fairly fast but usually longer distances i.e. 50+miles at a time. on a recent 1800 mile trip through France I managed to average 34 mpg using the best petrol I could find!! on one occasion I had to put in 20 litres of basic petrol and immediately noticed heavy pinking. I suspect the coupe body is better aerodynamically than the roadster hence better fuel consumption!
So far I have not noticed any deterioration as per Pete's experience will check the carbs and floats this week !!
Paul
P D Camp

Paul

Your suspicion about the better aerodynamics of the coupe is a fact well proven by the original roadtests. The 1500 will not do a 'two way' test ton while a coupe will.

Paul
Paul Dean

If you are getting a performance increase with the higher octane fuel, take that as a sign that you should not be running the lower octane! Unless you have a modern computer controlled engine with a knock sensor, which can retard the timing automatically, given two different grades of fuel that are both of adequate octane for the engine, you should not see a performance increase going to the higher grade.

I wish we could get super unleaded here. The highest grade of automotive gas available in Alaska is only 90 octane. You can actually get an "Alaska tune" for certain modern cars (mostly rice rockets) that require a higher grade than we can get, which is actually an "Alaska de-tune".

-Del
D Rawlins

Del,

The lower octane fuel is normal in parts of europe too - in Scandinavia the top rating in many parts is 95. Back in the ... the skimmed headed 1800s would only perform on 100 octane - not readily available with unleaded now - perhaps we should follow the advice we gave the Russians who had a problem with low octane fuel in WW2 - apparently the RR Merlin responded well to extra lead.... Still available in pellet form.

Neil,

The point about additives was raised over here a few years back. The supermarkets reacted very promptly by promising the same additives as the big boys. They wouldn't dare go back on their promise. If you get the press to raise the question in Oz, you would probably get the same assurance.

FWIW
Roger W

You can get ethanol-free gas in my part of the US (Puget Sound region in Washington) but it's usually at least 20 cents per gallon more expensive, is not available as super, and it's only produced by small local refineries. And knowledge of who sells it is pretty much by word of mouth. I put it in my riding lawn mower because the manual says ethanol-laced gas voids the warranty!
David Breneman

Most marinas have ethanol free gas. The rub is the pumps are on a dock and you must carry the fuel in containers.
Bill Haglan

This thread was discussed between 13/12/2014 and 17/12/2014

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