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Does 5W-20 Motor Oil Offer Fuel Economy Advantage over 5W-30?
 
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Question:
Does 5W-20 Motor Oil Offer Fuel Economy Advantage over 5W-30?
I have a 2003 PT Cruiser with the 2.4-Liter engine. Recently I looked up some research on how to improve gas mileage via driving habits, tire inflation, shutting down the engine for stoplights and coasting in neutral down hills. My fuel economy has improved from a paltry 24-25 MPG up to consistently around 27-28 MPG. I have been trying to get to 30 MPG, but can't seem to get above 29. I have read that using a lower weight oil such as Mobil Clean 5000 5W-20 instead of 5W-30 can improve my fuel economy. Recently Chrysler allowed the use of 5W-20 oils in 2005 model year vehicles. Some of these cars have the same 2.4L engine my PT cruiser has. Can you think of any reason the 5W-20 would harm my engine? Do you agree that I'll likely see a small improvement in fuel economy to put me over the 30 MPG mark?
-- Tom Stamos, Chicago, IL
Answer:
You should probably continue to use the viscosity recommended by the OEM (Original Equipment Manufacturer) which is a 30 grade. We have introduced two products: Mobil 1 0W-20 and 0W-30 Advanced Fuel Economy. We recommend you try Mobil 1 0W-30 Advanced Fuel Economy as a replacement for the 5W-30 you are currently using. By the way, an improvement of 2 mpg is quite significant and not likely to be achieved very easily, but you are doing the right thing by looking at tires, driving style as well as the oil you use.
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