Taxman· Premium Member
The tanker driver has to set the mix when he delivers, the detergents aren't in the big tank on the trailer.Why does the same Gas tanker that services Top Tier stations then drive across the street and service the non top tier stations.
For example, he might put 150ppm of the Marathon/STP additive package in Speedway's underground tanks and 400ppm of the same detergent in the Marathon station's tanks. (I'm working from memory and might have the numbers wrong, but there's a lot more of the stuff in Marathon gas than there is in Speedway) Then he drives to the Shell station and mixes entirely different additives in the gas he delivers there.
That's why it surprised me when an earlier post in this thread mentioned Speedway as one of the best fuels.
What's interesting is that all grades of Shell are Top Tier certified, but Shell Premium is advertised as having something like twice the additives as Shell Regular and Midgrade.
Around here, 93 octane costs 60 cents per gallon more than 87 octane, except at Shell stations where it costs 70-90 cents more than 87. Some of my cars that don't get driven much get Shell 93 under the assumption that it has way more detergent than is useful in normal driving. The low fuel light came on in my S420 last month and I planned on filling it the next time I drove it, but I haven't driven it lately so it still has 2 gallons of Shell I bought back in March. I should have filled it last week, now it's probably too late to get summer gas for it.