Cleaning out my car yesterday, went to open the trunk but I pulled the hood release instead. I thought well I’ll check the oil since it’s open. Level was down half a quart in 1800 miles. Never had to add more than a few ozs in the 5000 mile change interval before.
1.6 liter Hyundai accent. Last chance at 60k I switched to Pennzoil full synthetic. Had been using motorcraft semi synthetic. PCV valve still rattles and air blows easily thru it. One way only of course. Guess I’ll switch back to motorcraft next time. And keep a closer eye on it
Also I sent samples to Blackstone at 30 and 50k. All was good. Less than average wear according to the numbers
Half a quart in 1800 miles is very minimal. Only need to start worrying if you approach a full quart down in 500 miles.
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Yeah, I’d switch back unless you have a particular need for full syn. Oil consumption can vary a bit by brand/type.
But he normally burns 1-2 oz between changes. So, there is that.
Yeah the higher consumption seemed to start with the full syn oil. And it’s not leaking anywhere
That extra oil use may only continue for a short while. By the second change after going full synthetic it ahould stop. Full synthetic can do that sometimes on older cars.
Thanks for the advice. I guess I’ll run this oil up to 5k and watch it more closely. I really only switched to full syn for the cold start up advantage. Might should have left well enough alone.
Had y.ou checked the oil after the last change? If not, you don/t know if they put a half quart too littlle in it.
Hi Mustangman:
I’m curious.
Do you know what conditions would lead to synthetic to cause more oil consumption in an older vehicle?
And what happens to cause the higher consumption to stop?
I’ve heard people say to not use Pennzoil. They say it’s wax based and you get a glazed enigne or something like that. I really have no idea how much of this is true.
Switching to synthetic can cause a clean out of sludge if the engine was not well maintained in the past. It is from the extra detergents usually found in synthetic oil. If the car has an unknown past, it’s best to change the oil filter after the first 1000 miles when switching to synthetic.
Here’s a discussion if the differences between paraffinic and naphthenic crude oils. Paraffinic oils are better for lubricant distillation while naphthenic oils are better for gasoline production. Either works for both applications. It’s a question of efficiency.
I don’t know the answer but the theory is this;
I switched to Mobil 1 in a 96k mile Chevy V8 with Quaker State oil change stickers plastered all over it. The truck consumed a quart in 1000 miles and blackened the oil immensely. I changed it. Fresh change used a quart in about 1800 miles and I changed it at 2500. The truck used a quart in 3500 miles after that. I changed a head gasket later and it was a mess inside with chunks of crusty buildup.
I think the rings get cleaned up and start to seal better.
A buddy with a Toyota had the same initial results when switching to synthetic. A quart in 1000 miles. He immediately changed back to dyno oil and never considered sythetic again.
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I had a similar experience with a motorcycle. After about 5k miles I switched to synthetic oil to quiet gear clash on shifting. It worked wonderfully to quiet it down. However, it started consuming oil at an alarming rate whereas it had not used any prior. I mean having to add oil after almost every 100 miles. So I switched back and the consumption stopped but the gear clash was back…
I used synthetic in 2 used motorcycles I bought. I don’t remember either experiencing the oil use… but both shifted better with synthetic oil!
I’d guess if you stuck with synthetic for a couple more changes, it would have dropped back to normal. I told my buddy that, too, but he was not willing to try again.
Used machines, cars or bikes, generally have unknown maintenance history so the oil consumption problem with synthetic is either there, or not.
That may have been true 40 years ago. Today it’s just a Shell brand using similar feed stocks to everyone else.
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Maybe but it was practically new with 5k miles on it. It went on for about 2 weeks riding to work and adding oil every day. It would be clattering by the time I got home so the experiment was concluded early 
I was always curious why it happened. Were the ring gaps aligned? Was the cylinder temp really high in this design? Was the ring tension low? ?? IDK and likely never will. Still have the bike but haven’t ridden it in years now. Suzuki Intruder 1400.
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Thanks for that input. I was thinking along those lines as well.
But I haven’t resolved in my mind how an engine with initially sludged oil control rings that isn’t burning oil, suddenly begins to burn oil once the synthetic oil cleans the sludge off those rings.
Usually the oil consumption increases as the oil control rings get sludged up.
I don’t doubt it’s happening. I’m still missing a few pieces of the puzzle.
I think we all are!
We only have anecdotal experiences to try and understand this. And like @TwinTurbo’s experience, even some new engines were not happy with synthetics.
To answer a couple of questions, I change my own oil. I tried 2 Hyundai dealers and both overfilled with oil. 1 was nearly a quart over. And they used a cheap white label filter even tho they said they used oem.
And I bought the car new. No sludge.
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