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Synthetic oil for older inlines ?

20928 Views 44 Replies 29 Participants Last post by  Easy Rider 2

I tried synth in my 83 Kz750L. keep in mind that the motor has around 100,000 on it. It worked okay, but I started to get some leakage from the cylinder head and the clutch slipped a bit more than normal.

Other than that it ran fine. I wouldn't see any issues, but if I remember roght the YZF was liquid cooled correct? I'd think cheap old dino oil would work fine
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ONLY use synthetic oil if you have to have an oil that does everything better. It is really that simple. There is no voodoo or hocus pocus going on. It films and flows better and holds up better. It will not make your clutch slip and will not magically leak at every orifice. There is way too much myth surrounding this stuff.

From what I can tell, people with old worn clutches just don't want to admit that maybe thier clutch is bad and instead want to blame something else they don't understand. And if your engine leaks, shouldn,'t you fix it?

I ran Mobil 1 in my '78 XS11 with great results. My Vmax runs Amsoil with great results. If it was going to make a clutch slip, would't that show up on a powerful bike like my Max?

Oh, and the price may make your wallet drain faster too. But really, is it that much more?

I run my bike in near freezing weather as well as in hot traffic. Why not a good synthetic?

My opinion, of course

paul from Minnesota
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The Honda brand HP oils are pretty good, IMO (I believe that they are actually made by Mobil). I use the blend with moly and have been into enough dirtbike, streetbike, and racebike engines to be impressed.

26,000 miles is nothing. What did you think it would do, expire? Synthetic is marvellous stuff, but if engine longevity is your aim, then buy reasonable quality non-synth oil and change it twice as often. Even every 1000, if you feel like it - it takes ten minutes, costs only a few bucks, and you'll never need to rebuild the engine. Ever.
Go for it. Other than cost, and the possibility of finding some leaks that you did not know about, synthetics are fine for most any bike. Your wallet is the only thing that will take a beating, conpared to regular oils.
Ah cool, an oil thread....

I use Mobil 1 full synthetic in my w/c Trophy, either the MX4T 10W40 in the winter or 15W50 car oil in the summer. I've used either Mobil 1 or Castrol Syntec going back to the mid 80's when Syntec came out in a variety of air cooled and water cooled bikes with nary a hiccup.

If you want the best oil then use synthetic, either car oil or bike oil in the proper grade will hold up longer than anything else. I change oil at 6k per factory recomendations, use stock oil filters and full syn. oil and the bike runs as good at 30k as it did new.

Completely off-topic, but have you seen the new ST? The dealer saw how enraptured I was, and spared me. He didn't fire it up.

It was Silver.

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The only problem I've had with synthetic oil was notchy shifting with Castrol Syntec. I've had good results with Mobil1 and with RotellaT.
I use Mobil1 15-50 in everything I own. It works great and you can buy it at any Wal-Mart in the country. Do it.
Any modern oil (with current API spec), mineral or synthetic, should work fine.

I love synthetics for their cold-start protection and you really don't have to change them as often. They usually contain an additive that adheres really well to engine parts that eliminates virtually all engine wear. But even the mineral-based oils are really, really good today.

By the way, don't waste money changing your oil every 2000 miles; you don't need to, especially with synthetics and semi-synthetics (which are just about as good as full synthetics). I mean, if it makes you feel better, go ahead. But all modern oils are designed to last much longer than that (even if Jiffy Lube tells you to do it every 3000 miles). With synthetics you can actually go into the tens of thousands of miles, no problem.

And no, to my knowlege, synthetics should not cause clutch slippage or excessive engine leaking or clunky shifting.
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I use Mobil 15/50 in my old BMW, but it has a separate gear box. From what I've read most modern automotive oils do not contain an adequate amount of ZDDP (a zinc compound) to properly protect the gears which tend to destroy the long chain molecules in the oil, and thereby reduce the oil's protective qualities. The Rottela oil that seruzawa mentioned is formulated for diesel engines, and contains an adequate amount of ZDDP. VWW
My one Syntech experience was an immediate problem with notchy and difficult shifting when changing to SynTech on the GSX1100G. I drained it out and replaced it with Mobil1 after two days and the shifting problems went away immediately.

Another advantage I've noticed with Mobil1 is that my truck (has a 350 small block) doesn't eat as much oil. With mineral oils it burns about one quart btween changes (3000 miles). With Mobil1 it uses less than 1/2 quart every 3000 miles. Apparently the synthetic doesn't vaporize as easily when hot and get sucked up through the breather into the intake.
I was having problems with notchy shifting on my old CB350, and a buddy of mine who's a diesel mechanic suggested a switch to Chevron Delo 15wt 40 (from Honda 10/40).

Worked great, shifts line new now. The motor seems to run cooler also.

Now I run that stuff in everything. It's pretty inexpensive too, about 4 bucks a gallon. If you're an oil-change fanatic like me, that's means a lot.

If you rode Italian you'd be shopping for oil at your local deli.
The bike doesn't have bad mileage but it's 10 yrs old, parts look like they are going to be hard to find if anything major goes wrong, I am not sure about the bike's entire maintenance history... etc. etc. I figure that it wouldn't hurt to baby it at least until I can tear it apart and see how it’s held up so far.
I've used Amsoil with good results. Go over to and you'll find more information than you probably need.
Sorry to burt your bubble (and mine) Mobil1 15-50 (Red cap) is discontinued. Buy all that you can find.
Mobil 15W 50 In everything I own and will own.
Who the hell is burt?

Just went to Mobil's site and they are still selling it and didn't see anything about them not selling it in the future.
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