Hi everyone
My 2007 Outlander XLS FWD, got serviced about 2 weeks ago.
I use the iPhone app "Gas Cubby" to keep track of every fill-up and MPG per fill-up since I get my Outie.
It started with 16-17MPG and I even managed to get 18.6MPG out of it, but I noticed that when I changed my transaxle fluid, it went down to 15-16 MPG. Since the variation was not *that* significant, I just ignored it. On sept/04 It had an oil / filter, air filter and brakes change, and my MPG decreased to 14.6MPG.

Does anyone of you guys, have experienced something similar? And what could be the cause of this increased fuel consumption?

BTW, prior to the engine oil change it had 5W20 oil, and the mechanic changed to 10W40 SN certified (semi synth). I argued at him at first because I knew that factory recommendation is 5W20 but the mechanic told me that, the recommendation is true for the first 100K miles, and since mine has 107K, a "thicker" oil is needed...

So with this results I'm having second thoughts about the oil recommendation, because the decreased MPGs should be a symptom of something not good happening inside my car.

Any help will be really appreciated.

Thanks!

 

I agree with mechanic using 10w40 semi. It will have little or no effect on the MPG. I'd look for something significant like air filter or ignition components (plugs, wires) and even O2 + CAT. Look at what fuel running and try some higher octane.

Jim

 

Always use the proper oil recommended in your owners manual, if you are looking for higher performance you can use 100% synthetic.

 

Colder temperatures have seen my fuel economy start to come down as the vehicle runs at higher RPM's trying to heat up the cat.

 

I disagree with your mechanic. Use the correct viscosity oil. If you believe the oil is not doing its job, then you send an oil sample in for analysis. That will tell you if your 5w20 is not working. Going up in viscosity is a trick to reduce oil burning...only if you are burning oil. I have 155k miles and use synthetic 5w20 with no burning. There is absolutely no reason for me to be using 10w40.

 

Generally, you go up in viscosity due to main bearing clearances not because of worn rings. The 10w40 allows slightly more viscosity when cold but after it warms up it provides better lubrication due to the increased clearances on an 'older' engine. Its not a hard and fast rule and certainly analyising samples often indicate what is going on internally.jim