Would there be a problem if I started using synthetic oil on a car that has more than 180K?

 

No. If the car has been well maintained there should be no problems. If you have dried/rotted seals then the synthetic will expose it.

 

How do you know if you have bad seals?
I have 94k and want to switch also.

 

thats a good question... How do you check the seals?

I also saw some kind of synthetic oil that said that it was for high milage cars... What is that?

 

The only way to really know is to switch...should you start to leak you can:

A)put in a new seal
B)switch back to the old oil

My 91 Explorer developed leaks when I switched to semi-synthetic. Due to its age, I opted to switch back rather than fix the gasket.

The high mileage oil has extra additives to clean the engine and swell seals. Most on the board would tell you that it is snake oil. In my experience (remember the 91 Explorer) it slowed a leak I had on the car for over a year. I had two spots under the truck every night about the size of a half-dollar on regular oil. After switching to Valvoline high mileage, one drop disappeared the other went to the size of a dime.

 

i heard once you go synthetic, you can never go back.... is that a fact?

 

Sounds like B.S. to me.

 

Kind of like 'once you try...' oh never mind. Anyway, that's crap. If you want loads of oil information check out www.bobistheoilguy.com and browse the forums.

 

thanks guys!

 

once you try?...... whats the next line?

 

I can't really repeat it here....

 

As Spirilis says, it is (complete) BS.

Concerning the seal issue; a good quality synthetic will actually preserve seals better than your standard-fare petroleum oil as the synthetic will allow your engine to run cooler. Furthermore, the brand I am most familiar with has a robust additive package that keeps seals plump and pliable so they don't leak. Installing a good synthetic in your engine won't cause a leak; but if it is leaking now due to faulty seals, then it will continue to leak. Forget the "synthetics will leak because they're thinner" line I've heard tossed about...that's BS too. A 30-weight synthetic falls within the same viscosity parameters as a 30-weight petroleum oil. In fact, one of the advantages of a synthetic is that they will maintain their viscosity (and not shear back to a lighter viscosity) under extreme conditions. You will know if your seals are bad if your car is leaking oil.

If you try a synthetic and decide to switch back to petroleum, there is no reason why you can't. The brand synthetic I use is fully compatible with petroleum and can even be mixed with petroleum, if necessary.

I have converted many high mileage engines to synthetic with very good results. The key is that if the car had been previously well maintained and is not leaking, then there shouldn't be an issue.

 

I usually prefer Mobile1. What do you use?

 

I guess its that bad huh?

 

I use AMSOIL. Mobil 1 is a good product, but based on the test data I have read, AMSOIL offers much better overall performance when subjected to industry-recognized, API tests. Better resistance to oxidation; lower pour point, better high temp/high shear viscosity; ~ half the volatility (high temp evaporation); better ability to control acids; and 50% better wear protection. AMSOIL is about the same price as M-1 if you buy it right...

 

I was just considering the same question on my 110 k miles maxima. I think that over the course of the last 3k miles it has shown a small leak. Now I am not sure if maybe I neglected make sure that the level was all the way at high when I changed my oil last, but now it seems to be 1/5 th of the way down from H to C, or is it L... anyways I also smell a faint trace of engine oil smell in the morning on startup.
The waether has been very cold in the recent weeks so I havent been checking my fluid as frequently as I used to.

What should I look for if I am considering conversion to synthetic?

 

I recommend you carefully inspect your engine (including valve covers, the underneath side and the area behind the crankshaft pully) and see if there are any signs of leakage. Also, fresh oil drops in your normal parking spot are usually not a good sign. My experience with Nissans, and Maxima's in general, is that the material used for seals is of good quality. Unless your car has been neglected, it is likely the seals are intact. Concerning your oil level, it is difficult to get an accurate reading from the dipstick...keep an eye on the level and inspect for leaks. My experience with (leaking) oil smells is they are usually more noticeable when the engine is hot, rather than when it is cold. Hope this helps.

 

I want to switch as well. I have Walmart's high mileage full synthetic. It's crap oil, I want to go to Mobil 1 or something.

I have 145K and my car burns slight oil on startup and sometimes when I floor it. Should I switch? It is very very slight. I have checked the oil every so often and it is always full. I think it only burn oil when I get on it if I don't let the car sit and warm up first.

 

It's a personal decision, and it depends on the benefits you expect to derive. Also, as you have found out, not all synthetics are created equal. A good synthetic oil offer many benefits including longer oil and engine life, lower operating temps, better hot and cold temp performance and they can actually lower oil consumption in mechanically sound engines. If you're considering AMSOIL, I offer it to .org members for my dealer cost (~25% savings). Additional information is contained in the Group Deals section of this site.

 

I've had wonderful results with Mobil 1
93 Max, 230k (started mobil 1 at 130k)
97 Max, 130k (started at 90k)
2k Max, 130k (started from the begining)
93 Altima, 155k (started 135k)
95 Altima, 125k (started 109k)

None of them ever leaked. Idles better (more willing to rev too), possibly improved mpg. Always used genuine Nissan filters. oil changes every 3-5k.
Jae

 

The myth concerning synth oils causing leaks is a little bit of truth twisted with BS. Synth oils usually contain high quality detergents that clean the engine internals, including the seals. High mileage engines, especially those not regularly maintained, usually have a buil up of varnish, sludge, etc. built up around and in any space in the engine (including around seals).

What is theorized is that although a seal may have eroded over time, the build up of sludge around it, prevents any oil form passing (leaking). Once synthetic is introduced and the sludge is "washed away", the seal may start weeping, thus a leak occurs... which was not caused by the synthetic oil.

Disclaimer: I'm not an expert... just repeating what I've read in my many years of browsing oil boards and the like.