Hello Scoty, I been using mineral oil Shell Rotela 15-w40 on my Volvo semi truck D12D engine since I have bought it and it now has 700k miles!
Shell Rotela now have full synthetic 15-w40 and I want to switch to it so that I can go on fewer oil changes. Should I switch to the synthetic since the viscosity is the same? Thank you.
DON'T switch to synthetic with that high mileage! If you do, you'll likely start having issues with leaks. Synthetic oil is very thin and it will find it's way out of every crevice possible.
You have 700k miles on your truck. Stick to what got you there.
Why would there be leaks if the thickness of the oil is the same both are 15-w40?
Synthetic oil contains more additives than conventional, which high mileage gaskets and seals do not like. In the words of others, https://forum.ih8mud.com/threads/oil-leak-after-switching-to-synthetic.890551/
Ok,thanks man!
No problem! Hope you get another 700k out of it!
I hope so too 🙂
A few people in the topic you linked said the leak eventually went away. Maybe engines just need time to adjust to a new oil formula.
Sometimes but it is hit or miss. Most guys wind up having to try AT-205 or similar to try and swell the seals back up. I don't recommend it as it is a gamble. I try to avoid gambling anywhere I can when it comes to that stuff.
Keep an eye out for leaks!
Why would there be leaks ifthe thickness of the oil is the same?
Stronger/more detergents in synthetic oil will clean out more carbon and there will potentially be leaks by the seals where the carbon was built up. Me personally, I might try the synthetic anyways and keep an eye out for leaks or burning oil and if I notice those, switch back to conventional, ASAP. You might even need to use some AT-205 Reseal or a high mileage oil (which includes conditioners like that to swell the seals.)
Does anybody have actual evidence that synthetic oil has more detergent? I would think that synthetic oil generates less sludge, and therefore needs less detergent.
Honestly, I felt that synthetic oil was more marketing from the oil companies than anything else and I have not seen enough evidence to justify the higher price. If you have never used synthetic oil I wouldn't switch now. If mineral oil has worked this long just keep using it.
Trying to learn here, what would be the purpose of switching to synthetic if the truck had made it to 700K miles? Would a successful switch extend the life of the engine even more than continuing on with conventional oil? Fewer oil changes?
He made it sound like he wants to do oil changes less frequently or is interested in saving money by doing oil changes less often.
That's what I took away from it as well. But when you have a high mileage motor, and you start changing up maintenance to save a little money, it can really bite you in the end. Just not a good idea. 🙂
Ok I well keep it on the mineral, thank you for helping.
Synthetic oil has better better lubricating properties. Higher resistance to oxidation for longer oil life, and better temperature viscosity stability. So in theory it should prolong engine life.
Now, me personally, I have a 2007 Ford Ranger with a gas engine. 115,000 miles. High mileage for a consumer vehicle with a gas engine. Most of its life used synthetic blend oil. At about 90,000 miles, I switched to full synthetic. Then at about 110,000, I switched to Amsoil (only because I now put 15,000 plus miles on it a year and I want to see how far I can go between oil changes.) So far NO LEAKS, NO BURNING OIL. Before I changed to full synthetic around 90,000 miles, I did a couple short oil change intervals (I think I did a 300 mile and a 1,000 mile), instead of doing an engine flush. I thought it’d be safer and would clean out SOME carbon and clean it out more SLOWLY and CAREFULLY.
Has the oil always been changed as often as it should have been? Because if it has, maybe it’ll be fine. If not, you might start pulling too much carbon off places that’ll end up leaking.
Yes always between 11k and 13k miles trying to average 12k but we also do some idling hours maybe about 30 40 h in between this 12k miles interval
Like mentioned by James, the only reason it could start leaking from synthetic oil is due to its higher detergent additives it has compared to the conventional oil. A lot of older cars develop gunk and sludge which block leaks from being able to seep out of the seals and gaskets. Switching to synthetic could remove the sludge and build up after a couple of oil changes and hence you would possibly start seeing leaks. It has nothing to do with the viscosity of the oil it’s just the additive package in the oil. Also, just because you are putting synthetic oil in your car it does not mean you can extend the life of your oil changes. You still want to follow your manufacturer recommended service interval for your type of driving you do. Lastly just because is a 15w40 it doesn’t mean it meets the proper oil specifications. So I would check the back of the oil bottle and see if it meets your vehicle required specifications
I’m not recommending it, but suppose an engine has a minor leak and they go to a thicker oil. It MIGHT not leak as much or at all. I wouldn’t recommend doing this, though.
He can potentially extend the drain intervals. Send the oil to a lab, such as Blackstone, to have it tested, though. You might want to change the oil filter sooner, too, the first time. Maybe send a sample to Blackstone at your old oil change interval and change the filter at that time or even a little sooner than that. Just Incase it’s getting loaded with carbon from the cleaner oil.
Stay with the mineral oil unless you're a gambler withe seals in your high mileage engine.
Opinions vary, there is no right or wrong answer in this particular situation.
Yes I would switch.