roadfrog

Just posting my observations.

I am now at 11,000 kms (7k miles) on my current OCI. TGMO 0W20

I have added a total of 3 qts of oil.

1 qt at 6k kms
1 qt at 9k kms
1 qt at 11000 kms

Clearly, oil gets added more frequently as the oil ages. It would appear that the sweet spot for changing the oil would lie in the 8k km (5k mile) range.

I have no idea why this is so. There are no signs of oil burning (blue smoke) or leaks; old spark plugs were good when I changed them, and a compression check showed great numbers and within specs. "Doublebase"'s observations are similar to mine. In his thread, he stated that he'd be less inclined to do extended OCI's now and it sounded as though a higher viscosity oil didn't help either.

I'm not concerned, but I am perplexed. No amount of internet research shed any light on this phenomenon. This consumption is WELL within Lexus' specs as well as BMW, MB, and many others. As I've stated before, Consumer reports has done a story about new cars consuming oil regularly and can't seem to get manufacturers to explain why. VVT-I direct injection technology? Who knows.

So, my next step is to use my freshly acquired jugs of Castrol 5W30 full synthetic and post my observations. However, I don't hold much hope of an improvement, based on what Doublebase posted. I will likely just resort to going back to TGMO 0W20 next time if there's no improvement.

Post your comments and personal observations.

Rhambler

You can look at fairly known and reported issues that may hasten oil consumption. While I haven't been here long, I've seen people report valve stem seals or guides, which in itself could leak a minuscule amount of oil into the combustion chamber, not enough to smoke, but enough to notice a drop over time.

I'm not saying that is what's causing it, but what I'm suggesting is research known and reported issues that may affect oil levels.

Doublebase

Yeah that's something I thought of too, but what's confusing is that in my car I'll get virtually zero oil consumption for the first 3,000 miles...then I might add a half a quart at 5,000 miles, but after that on the way to 7,500 miles?? I may have to dump 1 and a half...maybe 2 quarts in. And that's all after 5,000 miles. Wouldn't the guides/seals not care about the mileage on my oil change interval? Perhaps the oil "thins out" as it goes longer, I don't know?

Doublebase

Roadfrog, I started a thread over at bobistheoilguy on this topic...got some interesting replies.

Most said...hey just change it at 5,000 miles, simple, problem solved. One guy suggested that he wouldn't even waste his money on synthetic oil if he was only going to be running 5,000 mile intervals, which actually made sense to me. He suggested a few high quality Dino oils that have excellent additive packages and are much cheaper than synthetics....motorcraft synthetic blend, Chevron, Penzoil yellow bottle. All have decent moly packages, all come in 5w20 and all are basically half what a quality synthetic would cost. I probably won't go this route because I just bought a year's worth of Mobil 1 for $2 dollars a quart through their rebate program.

Others stated that the direct injection and timing chain may be "tough on the oil". Fuel delusion was brought up, chain shearing the oil. High pressure fuel pumps shearing the oil. Who knows, but I imagine all that plays into it a little bit. And the direct injection is operating at high fuel pressures so I have to believe that there is some carbon being dumped into the oil...probably more than with conventional injection. I'd say this probably "dirties" the oil quicker. Does the higher soot content change the viscosity a bit and cause the oil to evaporate quicker? Some said that may cause it.

I'm running a mixture of Mobil 1 5w30 and 5w20 in my car right now....have 2,000 miles on the oil and of course the oil level is right where it's supposed to be, right at the full mark. I'll check it again at 3,000 and I'll be willing to bet it'll be down maybe a quarter of a quart, so I'll top it up. Then I'll check it at around 5,000 and it'll probably be almost 1 quart low...then I'll spend the next 2,000 miles putting another quart in, for a total of 2 - 2.5

One guy had an interesting take, he said he actually prefers his engines to "burn" around 1 quart on the way to 5,000 miles. He considers that good lubrication for the cylinder walls when the oil gets past the rings a little bit. Said he has torn down engines that burn just a little bit and there is less wear internally than on engines that don't. I guess that makes a little bit of sense, but then again if my oil didn't burn any oil I probably wouldn't agree with that assessment

roadfrog

Interesting observations Doublebase. Thanks.

703

Modern engine burn oil from looser tolerances to get better MPG.

But the V8 is not known to be one of them.