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(another) Synthetic Oil Question

Jun 20, 2002
Tallahassee, FL
none right now :(
This isn't Corvette specific, but I'd like opinions.

I just bought a Lincoln Town Car. 1996 with 116k miles. The car seems to be well maintained. I'd like to switch it to synthetic oil. Synthetic is all I even keep around at the house, as I use it in everything.

My problem is, do you think it will leak if I change with this high of miles?

I changed my truck after I bought it, and it started leaking (140k). This is why I'm a bit worried on this switch. I'm about to take a 3000 mile road trip with the lincoln, and would rather not have any issues on the road.
I thought Fords leaked from new.;) I changed my 90 vette over at 69k. about a yr after that I noticed my intake valley leaked just a little. I don't know if it was oil related or age.2 yrs later now leaks on my valve cover gaskets or any other seals . I can't say I have ever had any other cars leak when I changed them over and almost all had 100k plus. If your worried about it wait till you get back from your trip.Even if it does leak a little I don't believe it would be bad enough to cause you any problems.

synthetics do on occasion cause leaks, but its not the fault of the oil!
its the fact that theres a few gasket sealant compounds that tend to disolve, slowly or weaken under a constant bath of hot synthetic oil, that don,t do the same thing with mineral base oils, but in almost every case those sealants were never designed for use under that application
that yellow weather strip adhesive 3M sells gets used frequently by the older hot rodders, as valve cover gasket cement is a prime example

heres more OIL info






OK, so I will add these questions, I have one vehicle with 140K miles that I purchased new. Up until 130K +/- I changed oil every 5K miles. Now just because...who really knows why...other than advertising, I change every 3K.

The questions are these....

1. With better technologies than in the 50s, 60s, 70s, & 80s why is it supposedly necessary to change oil every 3K miles Vs 5K miles.

2. If the Vette, which uses Mobile 1, says change oil every year or 10K miles ~ which ever comes first, why wouldn't you use Moble 1 or =, in any vehicle. ;shrug


I guess the my first question would be "why", what would be gained from converting to synthetic on an engine with 116k miles on it. While the gaskets might be tight enough not to leak, I'm thinking it's 50/50 at best. I ran a 2 different Jeeps, one pick-up one a Grand Cherokee to nearly 200k miles on Havoline changed every 3-5k miles. Neither used any oil the day I sold them to someone else. I'm really thinking that the only advantage is the extended oil changes but truthfully the additional cost kind of offsets the savings. My C5 is on Mobil 1 but that was factory fill, and I won't ever chnge that to anything else. I bought a new Redline Vue last year and at the first oil change I switched it to Mobil 1. The difference there was it has a Honda engine, Honda recomends synthetic, Saturn fills it with non-synthetic....go figure. I thought I might pick up some extra fuel milage on the synthetic, but truthfully it didn't change at all.
the modern synthetic oils can EASILY go 10,000 miles between oil changes without a noticable loss in the oil quality, BUT--and this is important, the quality of the filters you use and how frequently you change them is important because oil traps and transports micro-crud and metalic dust, it gets difficult for the oil to work correctly if its carring any significant amount of crud, so Id change out the FILTERS at a minimum every 5000 miles
Please allow me to get up onto my soapbox! ;)

The NUMBER 1 cause of engine failure is HEAT!

Too much heat and you are looking at buying ($$$) a new engine. :cry

The NUMBER 1 advantage of synthetic oil is the ability to withstand HEAT. :_rock

The NUMBER 2 advantage of synthetic oil is the ability to decrease normal wear & tear to an engine. :_rock

Let's put the facts together.

Use of synthetic oil in an internal combustion engine gives you added protection against HEAT & WEAR and TEAR occuring in your engine! :upthumbs

Any questions, class?

I have notice when I changed to synthetic oil the engine temps didn't climb as high in hot weather. In very cold weather the engine cranks easier. The pour temp of synthetic oil is much lower than conventional oil so the engine gets oil to the bearings much quicker. When conventional oil is very cold the oil pump may not even be able to pump it, or able to pump very little.In Iowa we get the extrems, near 100 in summer and as cold as -30 in the winter. Synthetic is the answer here. Today it was 97 deg. I want that extra protection.

I also have a 96 town car that we bought as a winter car up here in ct. The wife drives a 97 MarkVIII in the summer. I bought the car off e-bay and it came out of deerfield park fla. it's got 70,000 on it. I have heard horror stories about switching over to synthetic on higher milage cars. My dad was a service manager for a ford dealership for a gozillion years before he retired.I still use that dealership for my ford issues The boy's down there tell me those 4.6's are bullitt proof, I wouldn't switch when you can go 5 or 6 thousand between changes. what I do is I use marvel mystery oil in the gas(I put it in all my vehicles) not alot!! and what it does is lubricates the upper cylinder walls,keeps your injectors (or carb) nice and clean,been using it for years. the only thing you should be concerned with is the intake manifold,ford had a class action lawsuit against them because it's made out of plastic and it's prone to cracking in the front right on the edge.I know mine did,and the date has expired on getting reimbersed for the repair.Also as for as engine temp on my ford's I been told by the guy's down at the shop to run a 192 degree all the time, Ifollow there advice and the engine's in the Mark and TC run perfect.
Suggest no one should switch to synthetic on a ten-year-old 116K mile motor. Your own truck experience should've driven the lesson home. And don't try RotellaT 15W-40 in the 4.6 lincoln ... we have two 98 TC w/4.6 ... I tried it and it's too heavy and tends to degrade emission components. Simply use a good filter & oil ... I'm now running WIX & plain Havoline 5W-30 in both TC. BTW ... good choice on 4.6 TC ... they're great cruisers and most folks won't believe the great gas mileage they get on highway. Yes the older ones (pre-2003 ?) have potential intake leak issues ... got that t-shirt.

BTW ... drove a friends 98 Continental coupla night ago ... his has the 32 valve motor ... it'll scat!

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