I was going through the manual recently while working on a friend's VW Jetta. The manual says "Use any API approved oil." or somesuch, with the appropriate S-rating. I dug through the manual and couldn't find anything anywhere that mentioned any more information. Apparently they don't care what viscosity you use.
I wonder from time to time if I'm running the correct weight oil in my turbo rotary. When I was investigating such things about 10 years ago, the conventional wisdom seemed to recommend 20W50, so I run Castrol in that weight. I don't even bother to try to crank the car in the coldest months. There were also those people who swore that you shouldn't use synthetic because of the metering pump. Anyone with good knowledge on this subject?
Sky_Render wrote: The new 5.0L V8 doesn't use oil pressure for cam timing, however.
No, but it does use oil, and the PCM's calibration is dependent on knowing how quickly the oil can go from one passage to the other.
1988RedT2 wrote: I wonder from time to time if I'm running the correct weight oil in my turbo rotary. When I was investigating such things about 10 years ago, the conventional wisdom seemed to recommend 20W50, so I run Castrol in that weight. I don't even bother to try to crank the car in the coldest months. There were also those people who swore that you shouldn't use synthetic because of the metering pump. Anyone with good knowledge on this subject?
Mazda says no synthetic because there was one brand that left a lot of ash, and since they couldn't say "Don't use Brand X" they said "No synthetic".
Likewise, 20W50, in my opinion, is more likely to cavitate leading up to the pump. Mazda kept making the pump deeper and this made it harder to fill, which is why they went to a dual inlet for the FD... But sidetracking here. If you have good pressure, use the thinnest oil you can, because the oil will flow through the bearings faster and cool them off better.
I used to use 5W20 with no problems. On the other hand, I think differently sometimes, like how I have this full-house 13B with a weeny tiny 12A oil pump on it, which is still plenty of pump and will cavitate less BECAUSE it's smaller. I also ported the snot out of the oil passages to and from the pump, as well...
Sky_Render wrote: So I add two quarts of slightly thicker oil for added insurance.
You'd be better off using straight 30 as your viscosity adder. It foams less than multi-viscosity oil.
Meh. I just run 20w-50 in the DD. In winter, i drop down to 15w-40 because a thin oil in winter is always nice. 
Knurled wrote:Sky_Render wrote: So I add two quarts of slightly thicker oil for added insurance.You'd be better off using straight 30 as your viscosity adder. It foams less than multi-viscosity oil.
That's actually not a bad idea. Now I need to figure out where to get straight 30-weight Mobil 1 from.
1988RedT2 wrote: I wonder from time to time if I'm running the correct weight oil in my turbo rotary. When I was investigating such things about 10 years ago, the conventional wisdom seemed to recommend 20W50, so I run Castrol in that weight. I don't even bother to try to crank the car in the coldest months. There were also those people who swore that you shouldn't use synthetic because of the metering pump. Anyone with good knowledge on this subject?
Rotaries are weird because of the oil injection. I used Idemitsu 20w 50 and Rotella T5 20W 50 in all mine and they loved. I also premixed 4 oz of 2 cycle oil (ashless) in the gas for lubrication.
This was on a bolt on FD and TII motor with a streetport.
The oil requirements are interesting for Euro cars, too. They have some dramatic change intervals to satisfy European no-maintainance customers, but then lower the quality requirements here, because Americans are cheap. Its sometimes worth the research to see what the Germans want at home.
Sky_Render wrote: Furthermore: ""If you mix viscosity grades such as a 5W30 low-viscosity oil and a 10W40 higher-viscosity oil, it is reasonable to expect that the resulting product will have viscosity characteristics which are thicker than the 5W30, but thinner than the 10W40. ..." http://wiki.answers.com/Q/Can_you_mix_motor_oil_viscosities
Be mindful it's not a direct relationship. You can't take 50% of Xw30 and 50% of Xw40 and get Xw35. It always ends up well on the thinner side of the expected average
Same brand and same formulation ONLY.
The SAE numbers are not exactly the most accurate anyway. You need to know the viscosity in cST at a given temperature (usually 40 or 100C) for both oils, to be able to math out the new viscosity in cST at that given temperature.
So, yes you can blend oil. No you can't expect it to behave like you're assuming. Especially going by the SAE numbers on the oil bottles.
some of the best conversations on bulletin boards populated with car guys revolve around oil... some people think that you are insulting their great grandpa when you tell them that what he put in his Model T isn't the same stuff you'd want to put in a modern car...
I work in a parts store and people come in every day and buy 10w40 for their ford that calls for 5w20 because that's what their dad/grandpa run I theirs.
208k on my dd and still running the original 5w30 with zero leaks and no oil usage between changes.
Meh.
I run 10w40 in everything irregardless of what the manufacture calls for. I buy it by the gallon or 5qt jug and buy whatever is on sale at the moment. That oil goes in everything except the lawn mower. My guess is the engines really don't care as long as it gets changed regularly. The last batch was Havoline.
You can run 0W30 in the dead of summer because it's still "30" at operating temperature. The "0" at start up temperature is still thicker than the "30" at running temperature.
Most 0w30s are also high detergent and have at least some PAO base stock. Win-win
Castrol Syntec 0w30 is the easiest to find in the wild. Made in Germany. Full PAO base stock, and not the refined dinosaur juice that most dept store "synthetics" are made of.
I go up a grade for an unknown engine that will be run hard. IE, my old Sunfire called for 5w30, I ran 10w40 year round for years all the way up to 192000 miles, beating it as soon as the temp gauge came off its peg, no problems. Yugo calls for a 40 weight but builds marginal oil pressure with it, this year it will get M1 15w50 upon revival.
Im not too hard on my 1ZZ Prizm, and considering the mileage and it doesnt burn appreciable amounts of oil. I can make a pretty good guess the bearings are still tight, so it gets 5w30 full syn.
Alan Cesar wrote: I was going through the manual recently while working on a friend's VW Jetta. The manual says "Use any API approved oil." or somesuch, with the appropriate S-rating. I dug through the manual and couldn't find anything anywhere that mentioned any more information. Apparently they don't care what viscosity you use.
I know if its a Pumpe Duse TDI, the oil type matters because LOTS of people have wiped out cams from running the wrong oil.
Sky_Render wrote: That's actually not a bad idea. Now I need to figure out where to get straight 30-weight Mobil 1 from.
Need to be careful with synthetics. Part of their advantage is that temperature affects the viscosity less, so a 10W30 or 5W30 synthetic may have no viscosity modifiers in it. That's the main advantage of synthetics, they need less additive to get the desired traits. Some oils are more than half additive.
Now, if you want wild, BMW specs a 0W60 oil for some applications. If you look at the spec chart for viscosity vs. the temperature ranges, the oil's viscosity stays almost constant. Wild stuff.
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