Best petrol for 32 Austin 10

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dnyoung
Posts: 6
Joined: Wed Nov 03, 2021 7:46 pm

Best petrol for 32 Austin 10

Post by dnyoung » Thu Jan 13, 2022 5:21 am

I’m in Australia and have been reading the suggested fuel options in the UK in the ATDC magazine.
Fuel options here are:
98 octane, 95 octane, 91 octane and E10 94 octane
I’m currently using 91 octane with a lead replacement additive. We don’t have E5.
What is the best to use?
Cheers
Dave Young

Rod
Posts: 70
Joined: Sun Nov 24, 2019 9:44 am
Location: New Zealand

Re: Best petrol for 32 Austin 10

Post by Rod » Thu Jan 13, 2022 8:02 am

I'm in NZ Dave, and I run my 14 on unleaded 91 (with no additives)-as did the previous owners to no apparent ill effect.
FWIW, my opinion is lead substitute additives are a cure for an issue which in theory should be problematic, but in practice rarely is.
Given the low power/low BMEP of the usual run of 1930s automotive engines, and the fact that the highest octane available pre war servo fuel was 80 RON (unleaded), I would anticipate that you will experience no undue valve burning or seat recession not using any additives, even if your car is a daily driver.
E10 fuel has its own issues with corrosion of Lead and Zinc based alloys, ATDC has a fact sheet on the subject which might interest you.
Others may have different experiences but that's my 20 cents worth...

dnyoung
Posts: 6
Joined: Wed Nov 03, 2021 7:46 pm

Re: Best petrol for 32 Austin 10

Post by dnyoung » Tue Jan 18, 2022 11:33 pm

Thanks Rod.
Thought the higher octane might improve performance without affecting the engine. It's a bit sluggish up hills but starts easily! Probably needs a de-coke. The engine is original and as far as I know it has never been worked on. Demonstrates the quality of the Austin engines - provided they are looked after. Certainly would not use E fuels but may give 95 a go.
Will check out the fact sheet.
Happy motoring in your 14.
Regards
Dave

Rod
Posts: 70
Joined: Sun Nov 24, 2019 9:44 am
Location: New Zealand

Re: Best petrol for 32 Austin 10

Post by Rod » Wed Jan 19, 2022 7:34 am

Wish it was as easy as upping the octane to improve performance! Without submitting a wall of text the most elementary explanation is that increasing the octane number above the minimum required in a specific engine will not improve the performance without adjusting the ignition advance mapping to take advantage of the characteristics of the fuel (all other specs for the engine remaining constant). The vastly simplified rule of thumb was the minimum octane number for a particular engine = 10 x CR, so a 7.5:1 CR engine would require something like 75RON fuel etc. In the case of a side valve engine it is very hard to improve the CR due to several intrinsic and inescapable features of the design, and radically improving performance generally without sacrificing the inherent flexibility and reliability is imo harder and more expensive than it looks. If you are suffering from an apparent lack of power over and above the normal A10's modest output I would respectfully suggest checking (if you haven't already) the basics like static ignition timing, operational distributor centrifugal advance (I'm assuming this model has such), valve clearances, coked up inlet or exhaust ports, compression pressures, exhaust restriction, correct carburetion (appropriate jets, float level, fuel pressure and/or flow esp for gravity systems) before invasive operations such as removing cylinder heads. If everything else checks out you may find a moderate advance from the standard 1/2 inch BTDC (or whatever your spec is) will achieve the results you need.

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peter_winney
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Location: BATH

Re: Best petrol for 32 Austin 10

Post by peter_winney » Wed Jan 19, 2022 10:12 am

Dave
Do you have another 10 owner near you so you can compare performance? As Rod says the Austin 10 is a bit sluggish up hills (mine can manage 9 mph when on the hill in the lane up to the racecourse whereas the Ford Fiesta can get up it at 30+ mph).

The Austin 10 gives you the opportunity to admire the scenery. In the Alps Maritime (where the mountain roads are less steep than the roads in the Cotswolds) have been passed by a cyclist going uphill.

If it starts well that suggests the valves are fine and do not need a re-grind.
Peter W
Member since July 1972
I ache, therefore I am

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