How often to change the oil?

[Lex]

I'm using Mobil1 5w-30 in my GTX motor and I was wondering at what intervals I should change the motor oil. Back when my car was NA and I was not using synthetic oils, I would do it once every 3000 miles. Should I do it less often now?

[goldstar]

With a fully synthetic oil such as Mobil 1, there is no need to change your oil before running 5000 miles. I use Red Line synthetic and change it at 5000 mile intervals.

There have been a number of threads on our Forum about this topic and at least one thread discussed the idea that synthetic oils actually lubricate better when used in extended oil change intervals upwards of 10,000-12,000 miles. Also, Mobil is now making an extended oil change Mobil 1 that appears to be the same as regular Mobil 1 with the exception that it contains a higher degree of additives and permits 15,000 mile oil changes.

Do a search and I think you'll find some interesting info about synthetic oils out there.

Happy Motoring!

[Lex]

but for good startup lubrication and good oil flow, isn't 5w-30 a good weight for a turbo motor?

[Tazman2]

Don't forget most filters aren't designed for the longer intervals either! And yeah even in my n/a EGT, 3k is the most i will go even though i use 5-30 amsoil 100% synthetic!

[goldstar]

The viscosity of an oil has nothing to do with its longevity as long as it's used within its temperature range. This is particularly the case with synthetic oils. If a fully synthetic 5W-30 oil is adequate for 3000 miles it's certainly adequate for 5000 miles. It's true turbo engines run hotter than NA engines but synthetic oils can withstand significantly higher temperatures without thermal breakdown than can mineral oils.

As a general rule, use the lightest weight multi-grade oil possible for startup and cold temperature conditions as long as the upper end of the viscosity range is adequate for high temperature, high stress operation. Synthetic oils permit extended viscosity ranges that tend to compromise mineral oils. For example, a 5W-30 mineral oil is not an optimal choice for best performance, for reasons I won't go into here, while the same viscosity range would give excellent service in a synthetic.

Finally, the FSM for my car specifies 10W-30 oil so that's what I tend to use. However, I believe that synthetic 5W-30 would be a more than adequate replacement and probably even a better choice in terms of extended fuel mileage, less internal engine friction and more suitability to the fairly cold winters we have in NJ.

That being said, turbo engines do run hotter than NA and if I had one I'd probably stick to 10W-30 just to be on the safe side.

Happy Motoring!

[Lex]

thanks for the info - it is very helpful. I do not beat on my car in such a way that it continuously runs hot - I like to keep my EGTs as low as possible, always turbo time and have a well working cooling system. From what I gathered here, I will change my oil at more than 3k miles and less than 5k. Next oil change, I will also switch to a 10w-30 viscosity.

[goldstar]

the FSM *doesn't* specify 10W30 for the GTX engine.... it specifies MANY different grades depending on temperature range

it's a known fact that heat cooks oil, synthetic or not... a turbo engine runs hot as hell, simple as that... thicker oil has a higher heat tollerance as physics dictates

no high tech **** or any marketing bull**** will ever defy physics

With regard to specified oil viscosity, I was referring to my 3rd gen, 2.0L engine, not the GTX engine.

No argument that heat is hard on oil, mineral or synthetic, or that turbo engines run hot as Hell. But I do disagree that thicker (higher viscosity) oil, by itself, necessarily has a greater heat tolerance. Polyalphaolefins (PAO's), the main constituent base stocks of Mobil 1 have a much wider temperature range, a higher viscosity index and greater thermal stability compared with mineral oils. Polyol esters, the main base stocks of Red Line oil have an even greater thermal stability and lower volatility than PAO's and consequently can extend the high temperature operating range and viscosity index of an engine oil even further.

My point being that a 5W-30 or 10W-30 synthetic oil will maintain its 30 weight viscosity rating at much higher engine operating temperatures than would an equivalent mineral oil. Therefore, it's not just the viscosity of an oil that determines its heat tolerance but also its inherent ability to withstand high temperatures.

This is certainly high tech **** but it's based on the real properties of synthetic oils so I don't think it's just marketing bull****. I don't see how any of this defies the laws of physics, either.

Getting back to Lex's original question about scheduling oil changes, greater thermal stability is just one of the reasons that synthetic oils allow longer intervals between oil changes.

[Lex]

Is there a method to determine the level of oil breakdown in an engine by somehow testing a sample? This way I could sample the oil at several intervals and assert its ability to lubricate at each point.

[goldstar]

Is there a method to determine the level of oil breakdown in an engine by somehow testing a sample? This way I could sample the oil at several intervals and assert its ability to lubricate at each point.

Check out: www.wihandyman.com/forum/showthread.php?t=16857

Happy Motoring!

[Denis]

but for good startup lubrication and good oil flow, isn't 5w-30 a good weight for a turbo motor?

It's so hot in Texas some times I run 20-50 in the summer.

[goodorange]

i've been using mobil1 10w-30 on my bp for about two years and just recently pushed it to 5000 miles and definately noticed a difference in the oil while changing. i'd only push it to 4000 this next time but just keeping up with oil changes regularly is really the key thing.

[Lex]

What kind of changes have you seen?

[goodorange]

black oil, at 3000 it looks like its almost right out of the bottle though

[goldstar]

There seems to be a tremendous amount of misinformation and uncertainty in regard to proper oil change intervals. First, lets look at the FSM recommendations for oil changes on 3rd gen, 2.0L engines. Remember, this applies to mineral oils as Mazda does not specifically recommend synthetic oils.

Schedule 1: (Normal driving conditions) U.S.A.
6 months or 12,000 km or 7,500 miles, whichever comes first.

Schedule 2: Canada, Puerto Rico and (Unique driving conditions) U.S.A.
4 months or 8,000 km or 5,000 miles, whichever comes first.
Unique driving conditions consist of:
Repeated short-distance driving
Driving in dusty conditions
Driving with extended use of brakes
Driving in areas where salt or other corrosive materials are used
Driving on rough or muddy roads
Extended periods of idling or low-speed operation
Driving for long periods in cold temperatures or extremely humid climates

I understand many of you don't have 3rd gen cars but I put this info up as an example. Use your own FSM's as a guide. In other words, even in what Mazda considers harsh driving conditions and using mineral oil, 5,000 mile oil change intervals are the factory recommendation. When I first bought my car, during the time the dealer was doing my oil changes, 5,000 miles was also the dealer recommendation.

Second, the physical appearance of the oil after a period of usage (how black it looks) is not a reliable indicator of its lubricating quality or a marker that the oil should be changed. The only way to judge oil quality or to gain insight into engine wear is through an oil analysis that also looks for the presence and quantity of wear metals in the oil sample.

Third, fully synthetic oils, not hydrocracked mineral oils that are sold as "synthetics" really are quite different than even the best mineral oils. Synthetics have many characteristics that make them superior to mineral oils. The one characteristic that is relevant to this thread is the fact that they have a MUCH greater operating life while still maintaining their excellent lubricating qualities as compared with mineral oils. If you accept the superiority of synthetic over mineral oils, it would seem wasteful and unnecessary to change it as frequently as would be the case with mineral oils in a daily driver, unless the car is raced, the engine is highly stressed from modifications or you are following factory recommendations for warranty purposes (as in my case, for example).

Fourth, the trend in synthetic oils is to engineer them for increasingly extended oil change intervals. Although Red Line has yet to produce such an oil, both Amsoil and Mobil 1 each have examples. For example, Mobil now has Mobil 1 Extended Performance oil that is guaranteed to go 15,000 miles between oil changes. Interestingly according to Mobil when using this oil, special filters or more frequent filter changes are not required (and this from a company that markets its own line of oil filters). Read about it at:

https://www.mobil1.com

Happy Motoring!