Ok, I just bought a basically one owner 90 GT a couple weeks ago. The owner has used SAE 30 weight Valvoline since day one instead 10W-30 as per Ford's recommendation. It's currently got 141,100 miles on the car. I'm wondering if that heavy of an oil would have damaged anything internally after being used for so long? I'm getting ready to switch it back to 10W-30 Valvoline. Thoughts? It's not burning any oil. Just leaking at the back of the valve covers.
Oil weight question
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z9_87
New Member
Just a heavier oil. That's what I run right now. If you have realy cold winters you might consider a lighter oil in the winter.
srothfuss
Last night I stabbed the same guy 7 times in a row
Actually the 30w oil has the same flow characteristics as 10w-30 oil when it's hot out. The only difference is that when it's cold out, the 30W will still be 30W and the 10W-30 will be 10W (thinner for cold)
As long as you live in a warm place you will be fine with a straight oil....
As long as you live in a warm place you will be fine with a straight oil....
illwood
Member
The magic stuff that is added to oil to make the multi-viscosity oil (i.e. 10w-30) is called polyisobutylene.
It is a polymer that has a super high viscosity and it acts differently depending on temperature.
Read the section on "Multi-weight oils" at the bottom of this page.
How oil works
It is a polymer that has a super high viscosity and it acts differently depending on temperature.
Read the section on "Multi-weight oils" at the bottom of this page.
How oil works
...that's word on the street...
Ummm, that's what I was going to say... yeah. Something like that.
Seroiusly, he's right. The problem with the polymer is that it weakens the lubercation qualities of the oil so regular SAE 30 is actually better unless you do a lot of cold starts. Basically your trading versitility for lubercation. However, with synthetic oils, that is not true, that is why they always are multigrade and better lubercated.
illwood said:
Ummm, that's what I was going to say... yeah. Something like that.Seroiusly, he's right. The problem with the polymer is that it weakens the lubercation qualities of the oil so regular SAE 30 is actually better unless you do a lot of cold starts. Basically your trading versitility for lubercation. However, with synthetic oils, that is not true, that is why they always are multigrade and better lubercated.
Ok, so you are telling my if I take a can of 10w-30 and bring it out of the 90 degree heat outside and stick it in my deep freeze for an hour its gonna get thinner? I am going to have to try that. I will pour it through a small funnel at 90* and try it again at 0* and see if it pours through faster. 
jerry beach said:Ok, so you are telling my if I take a can of 10w-30 and bring it out of the 90 degree heat outside and stick it in my deep freeze for an hour its gonna get thinner? I am going to have to try that. I will pour it through a small funnel at 90* and try it again at 0* and see if it pours through faster.
Nope, doesn't work like that. 10W30 is still a 30 weight oil, however it's cold vecsosity will be the same as a 10 weight oil.
So, to do the test right. Take some 10W30, SAE 30 and SAE 10 (hydrolic oil most likley). Heat them up, the 10W30 and SAE 30 will be about the same, the SAE 10 will be like water. Then freeze them to 32*F (0*C) and you'll notice the 10W30 and SAE 10 will be about the same, while the SAE 30 will be like a gel.
Michael Yount
Mustang Master
They're shooting you straight Jerry B - I'm surprised you didn't know that. The first number represents the weight the oil will behave like in the low temperature (32F) SAE test; the higher number represents the weight the oil will act like in the high temperature (212F) SAE test. The "W" means it's rated for cold weather service. So a 20W-50 oil acts like 20 weight at freezing, and acts like 50 weight at 212F. That doesn't mean it's thicker at 212 than at 32. It means it ACTS like a heavier viscosity oil when it's hot, and lighter viscosity oil when it's cold - hence the term 'multi-viscosity'. But in case you don't believe them -- just try Google with "oil viscosity". 
"Viscosity is the measure of oil’s resistance to flow. An oil’s viscosity is identified by its SAE’s (Society for Automotive Engineer’s) number. The thinner and oil, lower its number, e.g. SAE 10 W. The numerical relates to viscosity at particular temperature and the alphabet ‘W’, indicates the oil’s suitability for colder temperature. With the viscosity index improver, the viscosity increses at higher temperature and at lower temperature it does not increase significantly, thus achieving optimum viscosity at lower and higher temperature. Such oils are called multigrade oils, for instance ‘20 W40’ shows thinness at low temperature and thickness at higher temperature.
However, there are other service classification of oil apart from viscosity, developed by API- American Petroleum Institute, which indicates service characteristics. It is graded on a scale from SA (the lowest) to SJ (the highest) for gasoline engines, it is graded on a scale from CA to CG. Both the recommendations for viscosity and service classification can be found on label of the oil container."
To the original poster - I'd fix the valve cover leaks, and then switch it over to 10W-30 or 10W40 at the next change. At 141K with no oil burning - why would you be worried that some damage has been done? Seems to be running strong.
"Viscosity is the measure of oil’s resistance to flow. An oil’s viscosity is identified by its SAE’s (Society for Automotive Engineer’s) number. The thinner and oil, lower its number, e.g. SAE 10 W. The numerical relates to viscosity at particular temperature and the alphabet ‘W’, indicates the oil’s suitability for colder temperature. With the viscosity index improver, the viscosity increses at higher temperature and at lower temperature it does not increase significantly, thus achieving optimum viscosity at lower and higher temperature. Such oils are called multigrade oils, for instance ‘20 W40’ shows thinness at low temperature and thickness at higher temperature.
However, there are other service classification of oil apart from viscosity, developed by API- American Petroleum Institute, which indicates service characteristics. It is graded on a scale from SA (the lowest) to SJ (the highest) for gasoline engines, it is graded on a scale from CA to CG. Both the recommendations for viscosity and service classification can be found on label of the oil container."
To the original poster - I'd fix the valve cover leaks, and then switch it over to 10W-30 or 10W40 at the next change. At 141K with no oil burning - why would you be worried that some damage has been done? Seems to be running strong.
jerry beach said:Thats cool, good explanations guys.I am no expert on things, I just dont visit the shop for much of anything.
Hey, were all here to learn as much as shoot the **** right? I always keep in mind that it isn't if I know a lot or not, but I know enough to know, there is a lot I don't know. You know what I mean, Vern.
At least you asked, and now you know, instead of many which would have stuck thier head up thier rear and told themselves they know everythign.
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