On a cold start of my 1999 Rx300 AWD 65,000 miles. I will see about 5 seconds of smoke come out of the tailpipe. This may be a streatch but I think this has only started happening since I changed the oil to Mobile One 0w-30. Could the valve seals be leaking into the cylinders over a long shutdown? Comments?

 

Sure sounds like valve guides - that, or someone swapped a small block Chevy...

That 0W-30 Mobil 1 is likely the culprit. That's pretty thin stuff to put in a 65K engine. Unless you regularly experience extended sub-zero temperatures for a significant part of the year, stick with the 10W-30 product. You are probably getting excessive wear on start-up due to drainback of that too-thin lubricant. This is not a case of "if a little's good, more's better". Good luck!

 

What's the color of the smoke?

Salim

 

It's dark in color. Weird thing is that it only happens 1 in 10 cold starts. Could be just chance that when the engine stops turning over, it leaves a particular valve open. This valve has bad valve seal and leaks more than others. Not sure, how can anyone test a valve seal? Can they be replaced without taking the head off? I might pull the valve cover this weekend to check for gelling.

 

I have seen 5 seconds of smoke on occasion at start up, and I see that with many cars down here, both black and white smoke.

I have tried the following Mobil 1 weights, 5W-30, 10W-30, 15W-50 and now a 5W-50 (available only here in Mexico). I would never touch a 0W in any weight, either 30 or 40. That 0W flows 7 times faster than water. However, if you want, during the winter up in Mass., I am sure that could come in handy, but not during summer months.

 

A few seconds of smoke from the tailpipe after starting is not critical, but can be a warning of problems to come. White smoke is not normally a concern, usually the result of condensing water vapor. Black smoke usually indicates a too-rich mixture, and blue or blue-black smoke is normally associated with oil being burned in the combustion chamber. These are indicators that further investigation is needed. "Smoke" eminating from cooling system, AC system, crankcase breather (remove hose to PCV valve to check), or sustained smoke from any source signal needed repairs.

 

Lil4x is right.

A couple of other things you might want to check (and have been mentioned on CL) are the throttle body (might need to be cleaned), PCV Valve (also something that could be cleaned).

 

I'll put money on it its the valve stem seals. Same thing happened in my 2.2 liter 5SFE from Toyota in my MR2 after switching to synthetic, happens 1 out of 10 times and only if the car was sitting for periods of time.

Many Master Toyota Technicians swear it is not worth the money to fix as it won't affect performance or even emisions or fuel economy.

If you are really concerned get a leak down test done for $50, I did and I was less than 6% away from what a brand new engine was getting at 100,000 miles, Toyota can make a good engine.

You can also switch to Valvoline MaxLife and it will condition the seals back to life and also go with 10W-30 oil. After a few oil changes you'll barely notice it ever happening.

 

If it's blue smoke, it's oil getting past the valve stem seals. That's the usual indicator for bad valve stem seals getting hard and not sealing well. The change to synthetic may only be significant in that it tends to get past seals easier than dino oil, but the problem was likely there anyway, just masked.

If it's black smoke, it's a rich condition, could be a few things there.

White smoke, condensation, hopefully not because of a bad headgasket or coolant related.