Hi all, first post here. I live in Ottawa, Canada, and have a one year old Chevy Cruze Eco manual, with the 1.4L Turbo engine. The car has been great and is averaging 44 MPG for the entire first year of ownership, thanks to my careful driving habits and easy low speed commute.
The car calls for 5W-30 Dexos1 oil. I drained the FF at ~2500 miles (4000kms) and put in M1 5W-30. The OLM had me changing oil around 9950 miles (16000kms) based on my driving. I did so again with M1 5W-30 and a Delco filter. So far so good with roughly 13000 miles (21000kms) now. For the record, I have no loyalty to Mobil1 other than it was the factory fill in my Corvette (so I use there also) and it is cheap and easy to get when on sale at Canadian Tire stores.
I bought this car primarily as a fuel efficient commuter. I read through the "Oil University" posts here and found the information quite interesting WRT start-up viscosity and I'm wondering if I could use a 0W-20 in place of the 5W-30?
My primary driving is very easy, with the engine rarely ever getting above 2000 RPM. Our climate ranges from bloody cold to (relatively) hot and very humid. In the winter months my car barely and sometimes doesn't get to full operating temperature by the time I get to work, even with both upper and lower front grills blocked off and limited use of the heater. Other Cruze owners report oil temps over 250F in hot climates at highway speeds with AC use.
As far as I know WRT engine oil, four key differences that make this engine different from most are:
2. Small displacement
3. Water-to-oil warmer/cooler
4. Variable displacement oil pump
1 & 2 tend to beat up on oil, from what I understand, especially since the Cruze isn't exactly a light car (just over 3000 lbs in Eco trim). 3 seems to indicate that oil temps will rise faster and remain more stable than they would if the engine was not so equipped. Also, I use the OEM oil pan heater in the winter, though it's a low power 200W unit that does little more than keep the oil pan "warm". I do not have the ability to use the oil pan heater at work.
Number 4 is what puzzles me the most in this situation. The variable displacement oil pump operates to maintain a certain pressure to the lower crank case. An oil fed regulator varies the pump displacement and references the oil pressure after the main/rod bearings but before the cylinder head:http://vauxhall.workshop-manuals.com/astra-j/index.php?id=4646
WRT to engine efficiency: Would the thinner oil require a higher pumping volume from the oil pump to maintain the desired pressure? The way my mind works, this would make sense. If this is the case, would there be any efficiency benefit at all from using a 0W-20 oil over a 5W-30?
WRT engine protection: Would the thinner 5W-20 compromise engine protection at operating temperatures? With my regular driving style being so easy I would assume NO, but I would like to make sure the car is still capable of operating at higher speeds in higher temperatures. With crank case oil pressure regulated precisely by pump displacement, extra flow may be a benefit? Would the lower hot viscosity be an issue for the cylinder head or turbocharger?
Yes, I realise 0W-20 is not Dexos1 labelled… I'm not contemplating the warranty, I'm wondering what's best for my driving with an eye on efficiency and cold start protection. I put about 12000 miles (20000kms) per year on the car and would rather use the same oil year round if possible. Looking for the advice of the experts here. Thanks!