Oil question (another one)

[s2cmpugh]

I just started running 10w-40 to help reduce my oil burn off between oil changes, and so far it seems to be helping as less carbon accumulates on the back of the car (no blue smoke ever comes out).

The car currently has about 245k miles and runs great. I fixed ALL the external oil leaks. My question though, what about running 5w-40 synthetic on a higher mileage motor like mine that it's in overall good health? Any major concerns?

Thanks!
Cris

[STOCKa6]

It wont do damage, it will reveal any thats already occured though. Small leaks and worn seals will leak, worn parts may start to make noise.

I started my car on synthetic at 268k, nothing catastrophic, no noises, have replaced the seals and gaskets to stop old leaks and prevent new ones. I love it honestly, really cleaned up the top end of the engine.

Btw i use 3 qts honda genuine full synthetic 10w-30, and 1 qt lucas. If I burn oil in between I use HG syn-blend 10w-30

[wildBill83]

I wouldn't run full synthetic on an aged and worn motor. Your clearances aren't as tight.

The high mileage full synthetics may not get passed the pistons as easily as typical synthetics though.

[oyajicool]

10W40 conventional oil and 10W40 synthetic oil should flow at the same rate at given temperature.

Use 5W40 if ambient temp warrants the use for it.

[Raf99]

I wouldn't run full synthetic on an aged and worn motor. Your clearances aren't as tight.

The high mileage full synthetics may not get passed the pistons as easily as typical synthetics though.

Yep. The only other concern would be cost.

[wildBill83]

It's not the viscosity it is the molecular size difference that brings out leaks in older cars as well as the detergents that clean away gunk that is blocking leaks.

[s2cmpugh]

Exactly! Synthetic molecules tend to have less variation in size compared to dino oil so in a way more "leaks" might occur.

Anyway, I replaced all the external seals on the engine about 5,000 miles ago, so I'm not worried about those, but more about oil consumption.

With the massive amount of heat down here in FL, I thought running some 5w-40 synthetic might be a good idea, or 10w-40 synthetic.

Again, the motor does NOT blow and blue, black, or white smoke.

[oyajicool]

The high mileage full synthetics may not get passed the pistons as easily as typical synthetics though.

But you are suggesting the clearance between the pistons and what ever here (above).

Below is a link to a web site.

http://www.mobiloil.com/USA-English/...Oils_FAQs.aspx

[wildBill83]

If you made that far on dino blend oil then why not keep it up, if the motor is healthy it seems to be doing it's job. Dino blend is a mix of synthetic and non anyway.

If you decide to run full synthetics, you should change the oil and filter again after 2,000 miles, the synthetic will relocate deposits to your filter.

[Losiracer2]

I run the Mobil 5000 5w30 on my 273k mile DD. Even here in AZ, with temps regularly in the 115s sometimes, the consumption isn't at bad. Maybe 1/2-3/4 quart every 5k No smoke and the engine sounds healthy, doesn't tick at idle.

If you go synthetic, you'll definitely get a lot more valvetrain noise and the engine will sound louder typically. Conventional helps to bring the noise down somewhat since it fills in the clearances a bit more.

I usually buy one of those 5 qt. jugs at Walmart and it'll last me the entire oil change.

[Mishakol129]

I run the Mobil 5000 5w30 on my 273k mile DD. Even here in AZ, with temps regularly in the 115s sometimes, the consumption isn't at bad. Maybe 1/2-3/4 quart every 5k No smoke and the engine sounds healthy, doesn't tick at idle.

If you go synthetic, you'll definitely get a lot more valvetrain noise and the engine will sound louder typically. Conventional helps to bring the noise down somewhat since it fills in the clearances a bit more.

I usually buy one of those 5 qt. jugs at Walmart and it'll last me the entire oil change.

I have an oil leak that uses about that much oil, it doesn't consume it I don't think the engine was rebuilt not long ago. Its a leak I can smell it everytime burning off. Its been there since I rebuilt it and i've done everything to fix it; replaced the oil pan gasket, oil sender, dist seal. I'll have to do some more investigating. Maybe there's a gouge or something in the mating surface of a gasket, perhaps even the oil pump, balance belt or something, idk.


But I found that synthetic oil made my car run a little bit better, louder, but it leaked oil like a sieve. I use 10 40 and 20 50 to fill up after leaks.