engine leaks more w/synthetics?

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Oct 11, 2002
Pullman WA
If you have an older motor (4 cylinder) that seaps oil would switching to a synthetic oil make it leak even more oil? I've heard of people switching over to synthetic at higher mileages (over 125,000+ miles) with little or no problems, comments?
Well since you already have seepage, chances it will ge a little worse with the synthetic. If its a valve cover or oil sump you could consider snugging it up??
Depends on the car. I have a hunch that an iron block with aluminum head is more succeptible to leaking.

I put synthetic in a purchased-used MR-2 at 90K and it leaked like mad, externally and through the valve guides. Switched to valvoline max life and they went away slowly. Iron Block.

I put synthetic in a purchased-used Accord at 140K miles, and it hasn't leak one bit yet. Aluminum Block.
For conversation purposes, let's say we have a 10 year old truck. Truck has been in the family since around 96. It had, if I remember right, around 60k on the clock then. The truck now has 142k. Since we have had it, the maintenance has been great, change the oil and filter every 3-4k. While it certainly has not been babied (we originally bought it to tow a boat and I have loaded it up heavily a few times) it has not been over abused. The transmission has not even been rebuilt.

The oil I have used has been Valvoline 10-30 or even 10-40 when the 30 weight was not available. I had always read to find an oil and stick with it.

Switch to Synthetic?

I suppose what I am worried about is the oil film being thinner than before. Would the rings still seal? Would there be extra play in the bearings around the cam or crank? Should I go for a higher weight oil? I don’t have any oil leaks so I’m not worried a bit about that.
I don't believe in switching any engine with that high a milage. Just stick with what you are using. If you want to do extended changes I would do an auto-rx treatment and then oil analisis using your valvoline. If you are happy with that results then go with the synthetic but
analyze it as you extend the changes.
i know that many people talk abotu engine leaking more with synthetics but its only a few people.

question i have is. auto rx helped clean out my faulse seals and stop my oil leak from my oil pan seal. GREAT! but will going to syntetic reverse that. since synthetic is a little thinner than normal dino, wont it just start leaking again?

though ill probably try and run synthetic one time. probably my next oil change. i guess the only way you will find out is if u try. i just dont want it to undo what auto rx done to my seals.
If you guys are worried about using a synthetic in a higher mileage engine, why not try out Schaeffer Supreme? It's got the performance of a full synthetic, but with just 20-25% PAO in it you shouldn't have any concerns with leakage.
shaeffers is only an online order huh. i wish amsoil had a blend =).

yet you know how auto rx "fixed" my selas i just dont want synthetic to undo what autorx has done.

if thats ok then ill go with amsoil, i really am getting cautious of online transfers...i been attacked by hackers so many times.

[ May 02, 2003, 10:00 PM: Message edited by: digitaldrifter91 ]
I'm unsure of why there would be any more leakage with synthetic oil
Oil leakage is a product of defective seals ....not the flow properties of the oil that's leaking.

(a little flustered expression struggling to articulate)...let me try it from the other end ... are you saying that dino oil leaks less because of its poorer flow characteristics during start up?

Let's try point/counter point (lets have an exploring debate - totally healthy with smiles on our faces). Let's explore these statements and critique each one with a point or counter point.

I leak oil ..will synthetic leak more?

Fix the leak ..or live with it. What are your other needs in a lubricant? If you like synthetic so much ..live with the added expense. That is, if your engine/wallet would end up in the plus column ..why not? You are already wasting money by leaking dino ..if it's not doing the job you want what are you gonna do?

But will it leak more?

Why would it? Just because a synthetic oil has superior flow properties at given temperatures ..doesn't mean that it "necessarily" has any superior cleaning abilities. I would rather say that because of their superior temp/flow stability that most synthetics don't form deposits that are typical of other type oils.

But ..won't it want to leak faster?

Why? The volume of oil available to "leak" would be the same. Since most of the time the vehicle will be at operating temperature ..the flow characteristics of either dino or synth will be about the same (practically speaking). Lets take a valve cover leak ..or timing cover leak. Neither are pressurized lubrication environments. Why would a synthetic "want" to leak more? It will pass through the same opening at operating temp no easier than dino (minor distinctions apply).

But I've heard that if you go to synthetics ..your valve seals may start leaking.

This can happen with dino oil too. Again, I don't think that synthetics have any monopoly on cleaning action per se. Their main feature (IMHO) is that they have superior stability over broad ranges of temperature. My 92 Caravan has shot oil seals. When I use Shell el-cheapo ($0.85/qt.) ..they tend to stop leaking unless I'm really hammering it. One oil change with Pennzoil and the thing smokes at every stop light after warm up.

I think that the gap between dino and synth is getting pretty close for those who choose to "match them up" feature for feature. That is (I imagine), that you can find dinos that are just as good as synthetics EXCEPT in the extreme range of operation. I'm sure that someone could make a case that some dinos are SUPERIOR to SOME synthetics depending on the criteria of the comparison.

My view:

Go ahead and switch! You can probably have just as much effect with a variety of dino oils. That is, any negitive effect of synth ..can be stumbled upon with the right (or wrong, as it may be) dino.

Okay ..let's brain storm here. Assault my opinionated conclusions with zeal

Maybe you can

...or maybe

I'm more than willing to
if need be to the superior authority
patman: thanks i been on their site and never seen that. haha if it costs 10 cents less than pure synthetic then ill get the synthetic. though i dont think they sell that one here in tognotties.

gary: i see ur point. ok ill try synthetic. but gosh now i have to wait hehehe till the next oil change. only way to find out is to do it. o what a dummie, i get a discount on amsoil! hahah.

thanks for clearing things up.
Gary, you make some good points ..

... but I'd still play it safe (since the vehicle is already leaking a bit) and just use Pennzoil High Mileage Vehicle wich is a slight synthetic blend using esters (seal conditioners) instead of PAO. This might actually stop some of the slower leaks.

--- Bror Jace
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