Re: fuel
The definition may be similar but the tests are different. I figure the PON (what is on a US pump) to be about 4 less than the Research method. So what is on the pump may be 93 but the Research number would be 97-98.
I usually fill at 1/2 tank and aternate between 89 and 93 (today 93 at Sams was $2.20 9/10 (US pumps are always marked this way) per US gallon.
If mostly Interstate driving in the flatlands I may lean more to 89 since not at high load.
(nothing about the NA engine should need more than 87 PON but Merc always specs 91. Suspect that may be Research. but possibly results from the non-optimal plug location so I mix 89 and 93. Merc fixed in the next generation V6. )
What does the UK handbook specify please ?
ps the higher the octane the slower the flame propagation rate so 100 or 110 is going to need more advance than 91.
Last edited by Padgett; Jan 4, 2016 at 06:18 PM.