I'm having a hard time finding answers.... I recently did my first oil change using Amsoil 15W40 Synthetic Blend. My question is this... How many miles should the oil be changed? I am hearing some people put 15k on and send out for a sample.. Now I KNOW I can't go that long but it would be NICE to get 10K out of an oil change, maybe changing the filter and top off at 5K.. If anyone has any insight, I would greatly appreciate it!

I'm having a hard time finding answers.... I recently did my first oil change using Amsoil 15W40 Synthetic Blend. My question is this... How many miles should the oil be changed? I am hearing some people put 15k on and send out for a sample.. Now I KNOW I can't go that long but it would be NICE to get 10K out of an oil change, maybe changing the filter and top off at 5K.. If anyone has any insight, I would greatly appreciate it!

So you bought the PCO synthetic blend? With the blend I would do a UOA between 5 & 7k miles. If you don't want to do UOA then you could run it 7500 to no more than 10k and change it you will be fine at that if your running the EAO filter. If your running another brand filter you may want to opt for the OEM recommended OCI which would be right at 7500.

If you did buy the PCO I would switch it out to the full syn on the next oil change also, go with either the DEO or DME depending on if you want the 5W-40 or 15W-40. You could also use the AME if your truck is a pre-DPF truck or you have removed the DPF. The full syn is a higher quality base stock than the syn blend.

Let me know if you have any other questions.

Thanks! I am runninga Napa Gold oil filter 7202 I believe and will change over to the full synthetic next change. I'll probably do it sooner than later... (7k miles). I would like to keep running the 15w40 but this is only because it just sounds odd putting such light weight (5w40) in it.. But I guess it must be OK since a TON of poeple put it in..... I'm still new to the ideas of running full synthetic and being able to get 15k+ out of an oil change... Something in the back of my mind is telling me NO... Guess it's just habit.

I have been running 15w-40 in mine since I got it. I usually change filters @ 7500 and a full oil change @ 15000 with analysis every 7500. I run the bypass system and use amsoil filters. The DIC doesn't tell me to change oil until after 10,000 and it doesn't know whether I am running dino or syn oil. The analysis has been good over the last 55k I have owned the truck.

drhutch, what is your OI telling you at your 15,000 mile mark when you drop your oil? Is it still good for continued use (just curios as to how much is left at 15,000 with the bypass?). Thanks!!

No difference in weight when comparing 5W40 and 15W40. They are both 40 weight oils just have different cold weather starting points.