- Jan 4, 2016
My engine's oil cap recommendation states 0w20. I have been using Pennzoil 0w40 SRT for quite some time. Last oil change I switched to Mobil 1 15w50, just for S&G. I drive a lot and have a lot of idling time too. On average I go through 1 tank of gas per day. So if any changes take place - I notice them right away and can confirm if the change is permanent, or a one-time spike. Here are the results of Mobil1 15w50 in 2009 Scion xB: - Fuel economy did not take a hit over the past 7 tanks of gas, compared to the SRT 0w40. I was surprised, because I was under the impression that SRT 0w40 is a very "light" 40w and the 15w50 is a very "heavy" 50w. Expected an MPG drop, but that did not happen. - Really enjoying the smoothness of throttle response in the lower RPM range. Feels like the engine gained some torque. Can't explain why... Better ring seal?... BUT hate the slight HP loss in the upper RPM range. Very minor, but the loss is there. I will run this oil for 7k miles (my longest OCI yet in this vehicle) and will send it off for a UOA.