oil?

i know this is going to be a dumb question but what type of oil do you use in a GPZ 750? 10-30? 10-40? Does it matter?

I have no idea what the answer to your question is, but.....there are no dumb questions around here. Only dumb mistakes because the question wasn't asked first.

20w-50 castrol gtx.

Does it not have something cast into the oil filler hole cap?

They always recommended 10w40. You can use 20w50 but not in cold weather. I told my story about Castrol GTX in that I religeously change oil every 2000 miles, plus I was burning a quart of oil every 400-500 (165,000 mile KZ, worn ) So that's 8 quarts of "fresh Castrol" every oil change. You know what weight my 10w40 was in the end? Good question because I don't either. Removed the drain plug to drain, 2 oz of 90wt gear oil oozed out and that was it, rest was too sludged to even drain out. I have a couple cases of GTX sitting in the garage and I will not ever use it again. I guess just like when you get sick you think of the last thing you ate when in reality that is probably not even what it was. I think of the oil. This engine got real sick real fast.

I've only used the Bel-Ray 10w40 oil in my 82 GPZ1100 B2 with no problems (3000 miles between oil and filter changes).

Esso 15W40, without the fuel conserving additives. I've used it in every bike I've owned without problems. Change oil more on time than mileage, 2 to 3 times per year (less than 2k per change)

Yippeeeee another oil thread. I religiously use valvoline on my vehicles. 10w40 on my jeep cherokee and 20w50 on my 1000. Haven't found any probs with sludge especially with 3000 mile oil changes almost like you Ron! What brand do you use Ron?

I went to Shell Rotella-T 15w40. 15w40 is a diesel engine viscosity and I've used it in the diesel trucks for 20 yrs. So far it's worked great in that KZ650 I ride to work with 62000 miles on it. I got some valvoline 10w30 I'm using next Winter though as 15w is too thick in Winter riding at 10 degrees as I'm not driving that diesel anymore needless to say if at all possible.

NickW900LTD wrote:

20w-50 castrol gtx.

Back in the 80's, Castrol GTX 10-40 was the only oil that dealer's put in new bikes or bike's they serviced around here. It's very good oil and has high resistance to viscosity breakdown from shear effect. There may be better oils now, but it's still pretty good.

I still would not run any conventional oil in a bike more than about 2000 miles because of the gearbox shearing the viscosity enhancers turning 10-40 oil into 10W oil.

As for viscosity: 20-50 is good for hot weather only, 10-40 is good for cool weather, you can also mix it for 15-45W. Avoid any oil with "energy saving" on it because it has friction reducers that may gum up your clutch. Most 10-30W oils have this in them.

Here is a reference site on oil:

www.calsci.com/motorcycleinfo/Oils1.html

RonKZ650 wrote:

I went to Shell Rotella-T 15w40. 15w40 is a diesel engine viscosity and I've used it in the diesel trucks for 20 yrs.

Some of the references I have read say the "diesel specific" oils use higher grade viscosity enhancers which are more resistant to shearing effect, to enable the oil to run in trucks for very long service periods. That makes them ideal for motorcycle service. These additives also cost a lot more, hence the higher price of the oil.

Makes sense!