Q: Do our cars get used to one brand of fuel?
huzzsaba »
I have been using Canadian Tire Gas here in Canada for a few years now for my 2004 xc90 2.5t with close to 300k kms (approx. 185 k miles). I switched from Shell because of cheaper prices at Canadian tire, and because the premium at Canadian tire has no ethanol according to their website. It runs beautifully on Canadian tire Premium fuel and I have no intention to switch back.
Recently on a road trip, I filled up like I usually do at Canadian tire and got decent gas mileage that I usually get which is around 22 mpg. On the way back, I had to fill up at shell because there was no Canadian tire around, and I got the worst gas mileage in a long time which was around 18 mpg. It also felt like the car did not want to pick up speed.
I know from previous experience that Shell has good gas if not the best, but it possible that the car gets used to one and likes it better due to regular use.
A: No.
jimmy57 »
The engine control module (ECM) gets input from oxygen sensors and from the knock sensors that are info that has to do with fuel burn. If the fuel is higher in ethanol then the O2 sensor gives a leaner indication and the ECM adds fuel to get the input from O2 sensor within proper range. If the fuel is low octane (who polices octane of fuel against what is posted on pump?) then the ECM retards timing and then undoes the change to test for knock again. After a few knock “tests” that show high tendency for knock the ECM will adapt timing cylinder by cylinder until the level is found where knock is nil. This adaptive is load range dependent and is not long term. Periodically the ECM will tet for knock and will return to normal ignition mapping when knock is not longer present.
So the short answer is the ECM returns to normal baseline control of fuel and ignition if the fuel is good and “fixes” things when fuel is poor. Your routinely purchased fuel seems to be good fuel and the stuff you got on trip was not. High altitude fuel is lower octane. Buying fuel on the road in a place over 1250 meters altitude (somewhere in that range) and then driving onto lower altitude would trigger the adapative knock control functionality and yield reduced performance and more fuel consumption.
Do our cars get used to one brand of fuel?
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Last Updated on June 4, 2025
