is that synthetic 5w40 or dino 15w40? the one at napa is the 5w40 synthetic, thats why it is $16. autozone also has the 15w40 for under $10.
next time i think i will try the synthetic 5w40 from napa and see if there is a difference between the two.

 

Rotella 15w40 4 now.

 

I catch the dino Valvoline P.B. on sale at Advance Auto for around $8.00 a gallon and buy a case.

 

Hey..finally get to say a bit..been finding all sorts of good stuff here...Royal Purple is the way to go..check out the web site..awsome syn. outperforms them all...Think about it..nothing but the best for your CTD...

 

Im using the synthetic 5-40 so its a little more but still not bad at 16$ a gallon. during the warm months i will switch back to 15-40 dino premiem blue. Next oil change im getting the oil tested at black stone. I will see how it goes. as far as synthetic you will notice a difference. My cold weather starts were faster and seemed to be smoother. also when I swithed to the synthetic oil I noticed I had a little oil leaking from the crank case breather tube, weird, I never had that problem when I used PB 15-40. The oil level is right on all the time. No worries.

 

no $16 aint bad for synthetic. i use to pay $23-25 a gallon for mobil delvac 1 and it was really hard to find.

 

Why do you not use 5w40 synthetic oil year round? Not only does it give great cold weather starts but I would think that you would see better mpg in the summer time.

 

My understanding is that any oil, synthetic or dyno, breakdown on the high end of the viscosity much quicker if the spread is more than 25.
In other words a 5w-40 will turn into a 5w-30 sometimes before it's time to change oil.

 

I can see dino oil breaking down in between changes but good quality synthetic oil (I'm not talking about hydro cracked synthetic oils) should not do this in between oil changes. If synthetic did this I could not see this oil being approved for year round use.

 

All multi-vis oils from cheap to the best are approved for year-round use, depending on your climate, if you believe what's claimed on the bottle. For critical applications, don't buy anything based only on the seller's advertising claims. Advertising is designed to sell product, not to educate. It serves the seller, not the buyer. You didn't buy a Ford did you? You don't believe Furd's advertising claims, designed to convince everyone that it is the best, the most reliable, most sexy, etc. Ford even has "laboratory tests" backing up their claims. Motor oil advertising is the same. The only printing on the bottle which is not advertising is the API classification and viscosity numbers, and these are good only for fresh oil. What do the big trucking companies use in diesel engines expected to go a million miles between minor rebuilds? Delo 400 and Rotella. And yes, they take samples for lab analysis but this is mostly to detect defects in the engine, not in the oil.

 

Bingo.

 

Do you check oil vis as part of your analysis? You'll probably find the number increasing slightly.
I remember the first 10W-40 oils. They did not give multi-vis a good name. Luckily times change and so did oil technology. Most motor oil progressed from group I to group III base stocks which improved vis stability among other things. The marketing has stayed with the old times of 3,000 mile drain intervals required with group I & II basestocks.