Originally Posted By: vinu_neuro
Originally Posted By: dgcamero
I picked it up at the BoGo sale for my 2.0t FSI GTI...it seems fine, but I get significantly worse fuel economy in cold weather with it than the GC 0w30. I'll probably run it in the warmer months, and the GC 0w30 in the colder months for fuel savings.
What month did you switch from GC to 0W-40? Over the years a number of people on various forums I post on, including here, have complained about losing power switching to GC. I'm wondering how much additional loss with this Castrol euro oil.
I switched to the Castrol 0w40 in December. I bought it because it was on sale, they didn't have 0w30, and my car burns too much Castrol 5w40 so I avoid it unless I'm in a bind (and go to the dealer for their fill). We had a chilly November and comparable December. I drive fairly consistently, and it reduced my average winter fuel economy by ~1 mpg on highway trips and 1.5mpg on my commute! That's pretty comparable to Castrol 5w40. My theories, it could be attributed to the high pressure fuel pump on my car (thicker oil film on the follower?), and I have different all season tires this season (not LRR rated, nor was my previous set). Reason I think it's the follower is my trip computer's fuel economy calculator is considerably less accurate with an Xw40 oil in the car --- it worked very accurately with my initial dealer's Valvoline 5w30 MST oil fill and when I use Castrol 0w30.
I've never used Mobil 1 in my VW, and I'm stuck with Castrol as they had the most through and reasonable extended engine warranty program when my manufacturer's warranty was running out...but I couldn't tell the difference in the ML320 aside from only using 1 quart over 15k miles with Castrol 0w30 compared to Mobil 1 using 2 quarts. The 0w40 seems to be consuming less than the 0w30 in my VW.