Why does engines burn synth?

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I'm switching to Rotella-T synth. and have read about engines burning a lot of it once the owner changed. why? I want the cleaning effect of a HDEO, and would like to run 5w40 in my Ram V10, but don't want to start drinking it! Havve used M1 10w30 in the past, I believe it went through 1 quart every 3k. Don't believe it burns dino...
 
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Dont know if it's a myth or not, but I always found that my Hondas burned much more oil with synthetics such as Mobil1 as compared to a conventional oil such as Castrol GTX. I've heard it explained that conventional oil has molecules of varying sizes, and synthetic oil has molecules with more similar and uniform sizes. So it is more likely to get by rings etc.... . Dunno how true that is but I do believe there is some difference which makes Synthetic disappear quicker.
 

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I would guess some engines use more oil with synthetics because they are on the thin side. The 40wt should help prevent any oil burning issues you may have been having with a 30wt oil. Switching back and forth between dino and synthetic oil will not hurt a thing. If your truck does not like the synthetic oil you can allways change back to a dino oil.
 
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For what it is worth most vechiles settle down after the first oil change to synthetics. It is normal for them to use some oil the first time around on a synthetic. If this continues then the next step is to use a slightly thicker synthetic. My Dodge 4.7 V8 did not use any oil with 10W30 M1.
 
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New synthetic engine oil is highly detergent and when introduced into an engine that was run on a petroleum oil it can and often will use up all if its additives in a short period of time. Once the additives are gone the oil is less effective and an increase in consumption is possible. Keep an eye on the oil, if its gets dark really fast then it cleaning up contaminates or residue left from petroleum oil. It may be a good idea to use a engine cleaner prior to the use of synthetic oil and also change the oil the first time it goes down a qt. But I would not let some old wifes tales stop me for using it. Every vehicle can be different, how you drive and how someone else drives can be very different.
 
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quote:
Originally posted by Idrinkmotoroil: Dont know if it's a myth or not, but I always found that my Hondas burned much more oil with synthetics such as Mobil1 as compared to a conventional oil such as Castrol GTX.
I drove an '88 Civic for 150k miles on M-1 (95% 5w-30). I drove it hard in a hot climate. Car used no oil. Go figure. . .
 
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Actually, over the long haul, a Syn should provide a better ring seal and in general have lower volatility, given you match thc viscosity required for your particular engine. GTX dino has a pretty good NOACK volatility, so I can believe that it stayed in better than M1-5-30 in a normal situation, especially if GTX 10-30 were used. Viscosity and NOACK ratings are an important factor. Burning Syn is not what happens. If you are using Rotella, I would not expect any consumption issues.
 
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