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question about Synthetic Oil

2K views 10 replies 9 participants last post by  ryandamo 
#1 ·
Getting ready to start running synthetic oil in my truck wondering which is better the Rotella 5w40 or the Mobil 1 5w 40. and can you run the 5w40 year round or should I use it just for the winter months and go back to a synthetic 15w40 during the summer ?
 
#2 ·
I only run synthetic in my harley, i would rather run regular motor oil in my psd than synthetic. but thats just me, im sure someone else is running synthetic and can give you more insite.
 
#3 ·
5W-40 is a EXCELLENT choice for winter. I cant praise it enough. It will also help with cold starts in the summer by properly lubricating your engine faster.

The draw back is that the added conditioners that give 5W its high-tech characteristics WILL break down sooner than their 15W counterparts. They should still easily last longer than 5000 miles though while 15W synthetics probably won't break down until the oil is 20000 miles old and full of junk anyway.

There is absolutely zero harm in mixing or switching oils throughout the year, so there's no correct answer here. I would still run 15W in the summer just because it's a bullet-proof oil that won't break down.
 
#4 ·
i was alos thinkin about making the switch. with synthetics, you are supposed to do only 1 oil change a year, or about 10,000 miles.

i heard 5w40 synthetic is good year round. just be prepare to pay the up front price of synthetic oil. its like $30 a gallon.....and we need 3.5 gallons!
 
#5 ·
I use a Cenex 5W-40 available locally for about $15/gallon. But again, since 5W-40 is so loaded down with conditioners, I don't trust it past 5000 miles. The difference, especially up here in ND where air temps dip below -30F, is night and day.

Since my oil is black at 5000 miles anyway, I use the cheapest 15W-40 I can find in the summer. I don't need anything that lasts longer than that.

5W-40 is better than 15W-40 in any temperature from -100 to 250F due to a flatter viscosity curve, but you will be sacrificing some oil life meaning that it will lose its SAE40 protection while warm sooner than the 15W will.
 
#6 ·
The cenex is a blend. Its not a full true syn oil.


You can run a 5w40 synthetic year round. It wont hurt a thing. The 5w is only the cold flo rate.
 
#7 ·
honestly i think that synthetic is worth it, i got rotella 15w40 in one of my trucks and rotella synthetic 5w40 in the other, and the one with the 5w40 starts much better than the other one.

I have gulf coast oil bypass filters on both and will regular oil analysis at like 15 bucks a test i can run the oil indefinetly if i change the bypass filter every 5k miles. This helps keeps the costs of running synthetic down and highly recommend it.
 
#8 ·
My .02 Valvoline 15/40 year around! Synthetics i believe are a joke!
 
#9 ·
in my opinion, i would never run any oil past 5k, PSD's are incredibly hard on oil, harder on oil than any other engine out there........i think surpassing the 5k mark with any oil is putting the health and longevity of your injectors on the line......the 45 dollars i spend on MC oil and filter changes every 5k is the best money I can spend on my truck in my opinion
 
#11 ·
maybee your right, ive had good luck so far with my setup and my buddy with 600k on one oil change who got me into this stuff has also had good luck. the key is getting the stuff tested regularly for the statistics of wear, particulate, and detergent. if their good, theres no reason to waste perfectly good oil in my own opinion. my oil has not turned black once yet
 
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