OK this is a bit of a puzzler, for past few months have been running my 1999 S3 on Shell Optimax and Tesco 99RON, and my fuel consumption has gone from 360-400 Miles per tankful to 310-340 miles per tankful. I recently replaced my MAF as it was showing a low 170g/s and after changing it went back to 205g/s and the economy returned. my immdiate thought was ah it's the MAF thats been killing the economy, however, on the following three tankful things were back to 310-340 mile per tank. I have now discovered that the tankful I bought after replacig the MAF was when Shell had a shortage of Optimax and I remember putting in normal unleaded as I was needing fuel badly, the next 3 tankfuls were Optimax, last week I went for fuel and saw the price, and stuck in normal Shell unleaded, and low and behold my economy has returned, I've run two more normal unleaded tankfuls and got 365 and 379miles out of them. I can only therefore deduce that for some odd reason my S3 runs better on the cheap stuff. performance seems as good as ever judging by the "seat of the pants dyno" yet im definately getting better MPG. I drive very similar miles and routes each week so its not a case of different conditons affecting economy.
I'm going to stick with normal unleaded, but am curious if any of the experts on A-SN have any theories. Logically it should be better on Optimax but its not.
Nige
I'm going to stick with normal unleaded, but am curious if any of the experts on A-SN have any theories. Logically it should be better on Optimax but its not.
Nige
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