Scotty - My 2014 Chevy Cruze diesel used to get over 50 mpg routinely on the highway, then last November I had the oil/filter changed at a Valvoline shop. I gave them OEM filter to put on and they also put in a new air filter.

Immediately after that oil change, I started noticing my MPG dropped way down, down to about 38-40 mpg on highway trips. About 95 percent of my driving is highway. Suddenly I went from 50-53 mpg average to 38-40 mpg average. The motor runs perfectly though, starts up perfectly, has the same power, etc.... and no check engine lights have ever come on.....I cannot see anything under the hood that isn't connected as well.... so I'm stumped.....

I have had a new fuel filter installed, but it didn't really do much to help, maybe about 2-3 more mpg is all.

Do you have ANY ideas as to what happened? It is very coincidental that the MPG dropped right after that LOF at Valvoline last November. Makes me suspicious they did something (probably by accident) to affect it, but I have no clue what it could be.

I hope you can give some ideas. Thanks in advance.

lapointmw@hotmail.com

Mark LaPoint, Virginia, Minnesota

218-404-6839

Comments (2)
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MarkLaPoint
MarkLaPoint

Since that oil change last November, I went back to my usual place I get my oil changes and I know they use Mobil 1, dexos 2 full synthetic, 5-30SAE, which is what the manufacturer says to use. It still didn't change anything, still getting crappy MPG. It was at this same time I had the fuel filter changed out with OEM filter. I always use OEM oil and fuel filters too. These guys know me by name, I always go there for the last 15 years and have 3 vehicles so they see me all the time. After changing the fuel filter as well as the proper oil put in, the MPG is still getting much less than before last November. It improved slightly, averaging now about 40-42 mpg on hwy trips, but at least 10 mpg down from before. I can't figure it out.

ScottyKilmer
ScottyKilmer

Editor

they put in the wrong oil, diesels need DIESEL ONLY special oil, odds are they used a universal gas engine oil, only thing that would make sense