I know it's not a good idea to run synth oil in a high mileage motor, but???????

[The Shape]

Ok I have read quite a bit of replies around here saying that switching to synthetic oil on a high mileage engine will cause leaks. I have always ran Castrol GTX 10W-30 in my 115K mile GT. Lately though the oil pressure when the engine is hot hasn't been as good as I would like. So with summer and the 100 degree weather it brings coming soon I decided to go to a thicker oil. I got 5 quarts of Mobil 1 15W-50 that I paln to put in this afternoon. I am just wondering if the leaking when you switch from dino to synth oil issues will still be a problem since I am switching to a heavier oil. I am really not so much concerned with any new leaks as I am with oil consumption. Anybody ever have any problems with increased oil consumption switching to synthetic? I know I could have just went with a dino 20W-50, but my oil pressure was also getting a bit low this winter on days that it would get close to 40 degrees. That is why I wanted to go with something I can run all year long. The coldest it gets here in the winter is maybe the 20's on a few mornings, and from what I read on the Mobile 1 site this stuff should still circulate fine in those temps.

 

[Whytry91]

I've had three high mileage cars/trucks and I personally have never had any "leaking" problems, If you do spot a leak, it's just an indicator that you've had a problem the whole time, I don't think it causes leaks.
And I have not had more oil consumption either. It all depends on the condition of your motor, what's good for one isn't always good for the other.

 

[squeeeg]

I just put mobil 1 15w-50 in my car about a week ago. The only spots of oil i see are my valve covers(ok so whose dosn't leak) and where i spilled a drop or 2. nothing new, with 118xxx

 

[85_SS_302_Coupe]

Valvoline High Mileage in my car...someday when i rebuild it i'll recieve full synthetic, but not today.

 

[cevtv]

The only spots of oil i see are my valve covers(ok so whose dosn't leak)

Mine don't.

 

[NorCal66]

Same as squeeeg, switched to 15w-50 fully syn after using only conventional and had no leaks...cept the valve covers.

 

[The Shape]

Changed it out this afternoon. It seems to make a difference so far. I have a little more pressure at idle than I did with the dino 10w-30, but the real difference seems to be that I have about 50 psi at anything over 1500 rpm's even when fully hot. I was only getting like 37 when fully hot at 2000 rpm's. I took it out and drove it like I stole it tonight and even after beating on it pretty hard down some curvy backroads the least pressure I had at idle was about 27 psi. I will be able to tell how much it helped tommorow though I have to go to Memphis which is about an 85 mile round trip and it is supposed to be about 82 degrees. I am hoping it keeps good pressure. At the very least it should be protecting the engine better. I was kinda suprised how slick this stuff felt compared to the dino oil I am used to. I was expecting it to be pretty thick since it is 15w-50 , but it didn't seem much thicker than 10w-30.

 

[Ray III]

Mobil 1 is good stuff. When I put new rings and bearings in my dodge I put Mobil 1 5w30 in after the break in and the oil pressure did not drop from the 15w40 dino that had been in it, damn thing had like 70psi hot idle.

 

[HISSIN50]

The Shape, glad to hear you like the thicker oil. you hit one nail on the head -even though the pressure may not be as high, the oil does not break down as much, and even if it has the same pressure it did before, it is Protecting much better (clinging).

also, if you research it, i bet you find that the 15-50 M1 actually flows better cold than 10-30 or 5-30 dino oil, so you have protection on both ends. i know Michael would know this for sure. i know it is true of gear oils (Redline 80-140 synthetic flows way better cold than conventional 80-90 gear oil, as well as having much better protection and antishock properties when hot. best of both worlds kind of thing.

J., are you gonna go with an extended OCI?

i am gonna run some of the same viscosity in the stang this summer (normally run 20-50). think i will use a longer OCI.
i use it in the bikes and it does well (and they turn high rpm's, get hot, and have to deal with the transmission gears shearing the oil to all get out).

switching: i have switched a handful of cars over, and they did fine.

i think you made a good decision. enjoy!

 

[TheRedBlur]

well, I never ran a synthetic on my old old motors. but I did work at checker/shuck's/kragen auto and they told us not to recommend synthetic oils to high mileage customers becaus synthetic oils are more slick per weight than organics, and if you take a look, all the high mileage oils are pur-base, meaning organic based oils, with a crapload of additives. moreover, if you read the bottles of mobil 1 5-30's, 0-40's, or 5-20's they say that they are seal tested to not lead out of rear mains, valve guides, etc. meaning that they acknowledge that synthetic oils tend to slip past loose tolerances and seals easier.. but this just might be a bunch of marketing B.S. after all, I was nothing more than a professional pee-on.

 

[cardudeusa]

Valvoline just came out with a Synthetic verion of their Max Life. I put it in my car because it had a small leak from the front seal. If I let it sit for a day or two I would get a couple drops on my driveway. It has quit doing that now.

 

[Michael Yount]

The potential for leaks on higher mileage motors doesn't have to do with synthetics "slipperiness" - whatever that means. It has to do with its detergent properties. They tend to do a better job cleaning up varnish/minor sludge deposits inside the engine. In many cases these varnishes are filling up (and sealing) tiny voids in old/high mileage seals/gaskets. The synth comes along, cleans up that 'sealant', and Voila, you now have a leak. Doesn't always happen, but it happens often enough that its worth knowing about before you make the change. And now that you understand the dynamic at work, you probably also understand that the leak, if it's gonna happen, won't show up right after the change. If it occurs, it usually will show up weeks, or even months after the change - as the synth 'cleans up' things. So keep your eye on it - meanwhile, enjoy the summer driving there close to the Ozarks.

Those of you suffering with valve cover leaks, they can be made a thing of the past. Go to your local Ford dealer and buy a set of gaskets for a 96-2000 5.0L Explorer. They are metal embossed with rubber for sealing. They're nearly impossible to overtighten, they can be installed and removed multiple times, and they do not leak. Be sure everything is clean, and lightly lube the rubber/metal gasket with light grease - you just want it to slide and not bind while it's being tightened.

 

[85_SS_302_Coupe]

I've heard of using those gaskets, have you ever used Felpro rubber gaskets? I had those on my 351W and they were nice, leak free.

 

[Michael Yount]

It depends a bit on what's being sealed - oil, gasoline, exhaust or coolant. Given a choice between rubber and cork for the valve cover area, I'd take rubber; but even they are inferior to the rubber-embossed metal composite gaskets. It's too easy to overtighten the rubber-only gaskets crushing them, and squeezing them out in other areas. But if you're careful the rubber-only can work fine.

 

[04sleeper]

I use the stock Ford ones. Metal with raised rubber lip. They started using them on Mustangs in 91. I used to use these with my old car that had Solid Lifters. I used to pull my valve covers off once a month to adjust them. I also bought APR valve cover studs to make the job easier. They never leaked. It should be one of the first things you should do to a car if you haven't already. As far as Synthetic oil is concerned I would do what Michael Yount has suggested.

 

[MUSTANGJOE]

I switched to mobile 1 synthetic and a leak appeard about a month later on the oil gasket and the rear main seal ( I think! ) Im gonna get it fixed when I take it out from storage.

 

[battyice]

I've heard of using those gaskets, have you ever used Felpro rubber gaskets?

I've used the Felpro rubber ones, they were bright blue with metal inserts; I would recommend them to anyone. They're reuseable, and totally leak free.

 

[The Shape]

Well drove the car to memphis this morning. Temps were in the 80's and I had the A/C on. I purposely drove the car a bit harder than I normally do just to see how the pressure would do. It seems to have definently made a difference. I have a little bit more pressure at idle than with the dino 10W-30 (about 30-35 psi). But with the 10W-30 once the car warmed up fully on the interstate I would only see about 40 psi of pressure where as with the 15W-50 it never dropped below 50 psi. As far as the leaking I am definetly going to keep an eye on it since I already had very slight leaks from my rear main and from around my low oil level sensor. Normally when I change the oil I clean everything up under there and within 60 miles of driving I can see where soem oil has leaked out of the low oil level sensor down the side of the pan. I put about 250 miles on the car today and so far it is dry as a bone underneath. I figure though even if it does start leaking bad it just means I need to quit being lazy and fix them.

 

[mustang88GT]

I run 20W50 in my motor and have no leaking or oil consuption probs.. i did when i was runin 10W30... have no prob runin it year round, i was drivin it in the snow this year and had no probs. i put moblie 1 synthetic 15W50 and it seems to make it alot quiter, and it is a lil thicker than ATF so i think it should be better

 

[The Shape]

That is something else I forgot to mention. My engine seems alot more quiet at idle now.