It's time for me to do an oil change on my 2001 VW Jetta TDI with ALH engine. I have two quarts of Shell Rotella T6 5W-40 and I have three quarts of Mobil 1 Turbo Diesel Truck 5W-40. I'm thinking I'm just going to put them both in. Anybody see a downside to mixing them this way?
Mixing Rotella T6 with Mobil TDT
- Thread starter k1rod
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The ALH doesn't much seem to care what oil you put in it - many of them got gasser Syntec 5w30 for as long as they were serviced at the stealership. Run it with confidence for as long as you can stand it.
Thanks. I knew there would be some replies that would indicate to the effect "it's OK, but not the best", and honestly, I still don't understand the technical reasons for that. I'm guessing the thought process is that every manufacturer has optimized their formulation and by mixing two different formulations together you get something that is less than optimized??? But aren't these oils (in any particular class like HDEO 5W-40 Synthetic) built from the the same building blocks. I know the base stock may be different but Mobil seems to have no problem with mixing base stocks in various proportions to obtain their price/performance balance.
I do really like this ALH engine. It's got 205,000 miles on it and it runs like the day I bought it.
Thanks in advance for any insight.
I do really like this ALH engine. It's got 205,000 miles on it and it runs like the day I bought it.
Thanks in advance for any insight.
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Originally Posted By: k1rod
Thanks. I knew there would be some replies that would indicate to the effect "it's OK, but not the best", and honestly, I still don't understand the technical reasons for that. I'm guessing the thought process is that every manufacturer has optimized their formulation and by mixing two different formulations together you get something that is less than optimized??? But aren't these oils (in any particular class like HDEO 5W-40 Synthetic) built from the the same building blocks. I know the base stock may be different but Mobil seems to have no problem with mixing base stocks in various proportions to obtain their price/performance balance.
Mixing the base stocks isn't so much of a problem, it's mixing of the additive packages that the oil formulators don't like.
Thanks. I knew there would be some replies that would indicate to the effect "it's OK, but not the best", and honestly, I still don't understand the technical reasons for that. I'm guessing the thought process is that every manufacturer has optimized their formulation and by mixing two different formulations together you get something that is less than optimized??? But aren't these oils (in any particular class like HDEO 5W-40 Synthetic) built from the the same building blocks. I know the base stock may be different but Mobil seems to have no problem with mixing base stocks in various proportions to obtain their price/performance balance.
Mixing the base stocks isn't so much of a problem, it's mixing of the additive packages that the oil formulators don't like.
Originally Posted By: SilverC6
Why not just go buy 5 more quarts of oil so you have two complete changes, one in each brand.
Problem, imagined or real, solved.
If it turns out that is the right answer, that's exactly what I'll do. But I'm asking the question even more to get an understanding of the nature of this than I am to decide a course of action.
Why not just go buy 5 more quarts of oil so you have two complete changes, one in each brand.
Problem, imagined or real, solved.
If it turns out that is the right answer, that's exactly what I'll do. But I'm asking the question even more to get an understanding of the nature of this than I am to decide a course of action.
k1rod.
the miscibility standards for engine oils is that they mix, and can be subject to cooling to the (new) pour point, heated to 150C and cooled again to the pour point.
During this process, the new mix must not separate, or form a precipitate. And as they can't find and mix every oil on the planet, the tests aren't with every oil on the planet, but simply with 7 standard reference oils.
But there is no promise whatsoever that mixing two 5W40 CJ-4 lubricants will result in a 5W40 CJ-4 lubricant. The 40 part will most likely stay, the 5W part might stay, but the specific and engine tests that make up the "specification" are up in the air.
You can mix, and chances are very high that you won't have anything nasty happen. However it's extremely unlikely that the mix is as good as either of the components.
the miscibility standards for engine oils is that they mix, and can be subject to cooling to the (new) pour point, heated to 150C and cooled again to the pour point.
During this process, the new mix must not separate, or form a precipitate. And as they can't find and mix every oil on the planet, the tests aren't with every oil on the planet, but simply with 7 standard reference oils.
But there is no promise whatsoever that mixing two 5W40 CJ-4 lubricants will result in a 5W40 CJ-4 lubricant. The 40 part will most likely stay, the 5W part might stay, but the specific and engine tests that make up the "specification" are up in the air.
You can mix, and chances are very high that you won't have anything nasty happen. However it's extremely unlikely that the mix is as good as either of the components.
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