Oil for 1981 KZ750LTD 4 cylinder

Hello, I have a 1981 Kz750 LTD 4 cylinder and was wondering what the best oil and viscosity to use is? Thanks

I can't say what is best. I have been using Rotella. White jug 15-40 or 10-40 not sure as I'm not at home.

As far as I know the white jug around here in North Dakota is 15-40. Right now the bike has 10-40 mobil clean 5000. I was just wondering if running a thicker viscosity would be better or not

You will get tons of different opinions on this, but consider the following. In the good ole days cars oils worked great; I was a big fan of Castrol GTX. However, over the years the formulas for car oils has changed. ZDDP (phosphorus) which deposits a sacrificial layer on parts that sustain high pressure to protect them (such as cams in KZ engines) has been removed (by law) from automotive oils. The reason it was removed is that ZDDP is not good for catalytic convertors, and all cars now have them. In its place a variety of "friction modifiers" have been added to car oils. These work great for cars. However, unlike cars, KZ's have wet clutches that are bathed in the engine oil. These friction modifiers have been known to reduce the friction needed for a wet clutch to operate properly, so they are not good for KZ clutches. The latest oil standard for motorcycles is JASO MA. Oils that are marked as meeting this standard do not have the automotive friction modifiers and work fine in KZ engines. Synthetic or dino oils work in our engines as long as they meet the JASO MA (not MB) standard. If you look for motorcycle oil you will find oils meeting that standard; car oils do not meet this standard. I prefer synthetic and use Mobil Racing 4T, but there are other very good JASO-MA rated oils out there.

I suggest you spend a few minutes looking through the internet at discussions regarding "JASO-MA"; just do a Google search on it and you will find tons of info. I think that will help you decide not to use car oils.

Regarding switching to a higher viscosity oil - unless you live in a VERY hot climate (not North Dakota) I would stay with the recommended 10W-40. When you start a cold engine you need all the lubrication you can get and that's where the 10 in 10W-40 comes in to play because it flows better at cold temperatures than 15W-40 oil. Bigger numbers don't necessarily mean better protection. Keep in mind that guys with new Corvettes are running 5W30 and even 0W30 oil - but I wouldn't put that in a KZ. Ed

Best Oils To Use In Your Bike (Just My Opinion)

Engine oil : The commercial grade oils are clearly superior to the mass market oils. For the best protection in your bike or car, use Shell Rotella Synthetic, available at Wal-Mart in blue containers . For the best petroleum oil you can buy, get Shell Rotella T, Mobil Delvac 1300, or Chevron Delo 400, available at any auto parts store. On the back of most oil cans is a circular stamp with the certification. Avoid oils that say "energy conserving" in the bottom half of the donut.

These oils contain friction modifier additives that could cause clutch slipping over time. The EPA mandated certain gas mileage, so the auto makers turned to the oil manufacturers who came up with friction modifiers of the oil to meet these new standards. All XXw-20 and XXw-30 oils are energy conserving, and should not be used in your motorcycle. Don't buy any oil additives like STP or Slick-50. Here's several listings on all about oil justifying these conclusions.

The Recommended Synthetic Oils :

Shell Rotella Synthetic
5w-40 Delvac 1 Synthetic
5w-40 AMSOil AMF Synthetic (pricey, but it’s your money)
10w-40 Golden Spectro Synthetic
10w-50 Motul 5100 Synthetic
10w-40 Mobil-1 Synthetic
15w-50 Mobil-1 MX4T Synthetic

The best synthetics are: (in no particular order)

Shell Rotella-T Synthetic 5w-40 (blue container is synthetic, not white which is dino), gallon at Wal-Mart.
Mobil Delvac-1 5w-40 (grey container is synthetic, not black which is dino), gallon at Petro stations, gallon at Farm and Fleet.
Mobil-1 SUV 5w-40, qt anywhere.
AMSOil AMF 10w-40 synthetic motorcycle oil. (again, pricey)
Golden Spectro Supreme, (no price).
Motul 5100 Ester, (no price).

Mobil-1 automotive oils all contain small amounts of moly - about 100 to 200 ppm. This can cause clutch slippage in some motorcycles. I've only heard of this being a problem in Honda Shadows.


The Recommended Petroleum Oils

Chevron Delo 400 15w-40
Delvac 1300 15w-40
Shell Rotella 15w-40

The best petroleum oils are: (in no particular order)

Chevron Delo 400 15w-40 (blue container) gallon at any auto parts store, gallons at Costco.

Mobil Delvac 1300 15w-40 (black container) gallon at any auto parts store, gallons at Sam's Club.

Shell Rotella-T 15w-40 (white container) gallon at Wal-Mart or any auto parts store, gallons at Sam's Club.

Castrol 15w-40 (Green container) gallon at Wal-Mart or any auto parts store, gallons at Sam’s club.