Dealer Oil Change & MPG

The last 2 oil changes I've done I have instructed the dealer to use Mobile 1 5w30. Since doing so my average mileage according to the computer has been around 12.5

Before leaving on a trip last week I had the oil changed. Service advisor called me to come pick up the truck cause it was done and then proceeded to tell me the service tech said the 5w30 M1 was too thick for the tight tolerances of my engine and it needed 0w20. They ignored my instructions and put in the 0w20. I know it's not the end of the world and said whatever. I live in FL. It's 90+ every day now. My mpg never got above 11.6 The engine seems to like the M1 5w30?

 

I don’t see why you would get better mileage with thicker oil, but I also don’t think it’s going to do any harm, which ever one you choose to use. I think the second generation 07 through 13, required that weight oil, they only changed it to 0w 20 in the current model. I may be mistaken, but that’s what I recall.

Also I only fully trust hand calculated MPG’s as opposed to what the computer says. Do you reset the average mpg every time you fill up?

 

I agree with the hand calculation but this is a solid 1 mpg loss according to the computer. It does mean something. I have never reset the mpg on the computer. Didn't know I could. I will try it.

 

To reset my average in my 15, hit the display till it’s showing average, then press and hold display to reset.

 

Tight tolerances sounds like a BS excuse. The 5.7 is the same engine for a very long time. The standard oil a few years ago was 5w-30. If tight tolerances were a big concern, the manual would not have 5 different weight oils listed as acceptable based on circumstance. Tolerances magically got tighter the same year CAFE reared its ugly head? I think not.

 

Heavier oils are called for in hotter climates/countries-Mexico for example. They don't make a different engine for those places, you are fine. Thinner oil would theoretically give you better mpg, not worse. I wouldn't worry about it. These trucks suck for MPG.

 

Well, since it is hotter now, perhaps your AC is working harder. And yeah what the dash read out shows me is never close to my pencil calculations. I wish it was because two 10-mile trips this morning, mostly interstate, showed 18.8 and 19.2....with AC running (90's, every humid). But I do expect this tank to be above 17 now since I consider it broke-in with over 600 miles on the odometer.

 

The dealer could've let your truck sit and idle for a time. That'll bring your average down real fast.

 

Maybe they didn't want to put a weight in not specified in the manual?

 

I've never gotten any pushback before on the request. They just say that will be extra. It's really just something I noticed. I will say I have never seen anything above 12 on the computer until I started using the 5w30 M1. Really does not matter it's just an observation. The 0-20 in this climate is too thin IMO and we are probably splitting hairs with that statement.

 

If that was the case then half of us are running the wrong oil.

 

Probably.

 

The difference between the oil weights will never ever effect mpg that much.