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MG MGB GT V8 Factory Originals Technical - Rover 3.5 fuel grade?

What's the best fuel octane to use in a stock 3.5 Rover? I looked in the archives but nothing there.

I finally got my project licensed and back in the garage due to an unexpected snowstorm in the Vancouver area, but as soon as the sun comes out, out she comes and will need a full tank of gas shortly.

Cheers
Simon
Simon Austin

Whats your compression ratio and altitude of where you live?
Jake

Engine rebuilt to stock, manual says 9.35:1 and Sea Level. Chances of climbing to altitudes up to 3000' assured as we have to climb mountains to get out of the Lower Mainland.
Simon Austin

I've found mine very tolerant of low octane, but then it is the factory 8.26:1. My 4-cylinder 9.0:1 pinks badly on 'standard' 95 unleaded, just about OK on Super 98. It is very much a factor of combustion chamber design and different examples of the same spec can vary greatly. With very different fuels to the original when the manufacturers came up with the specs the best thing you can do these days is adjust to specs and try different grades. If it pinks on the highest available then you may have to retard a degree or two, but as I say the V8 is not known as a 'pinker' in my experience.
Paul Hunt

Hi Simon

For crusing around the Coast I use regular gas with the odd tank of premium thrown in. Before one of our 2 yearly drag race’s up here on the coast I will run a couple of tanks of premium through.
When I go on a trip over the Coastal Mountains I use Premium. I will usually fill up out in Abbotsford as the cost of premium is the same as regular up here on the Coast.
Does it run any better? It does run fine on regular but I think the premium smoothes it out a bit.
The best way to find out, run a tank of regular through and then try the premium. The highest Octane is available at Chevron.


Bruce.
Bruce Mills

Thanks gents. Now if the snow would melt, I can get her out of the garage.

Cheers
Simon
Simon Austin

Note that since the V8 has alloy heads, the CR can be much higher than a cast iron head - 11:1 in an alloy head wil run on premium fuel (98 octane) - so 9.35:1 will be OK with regular fuel (93/4 octane)
Chris at Octarine Services

This thread was discussed between 08/01/2005 and 10/01/2005

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