New Member with a gear oil question

[climbersteen]

Hi, name's Dick and I am new to this forum but have ridden BMWs for way over 30 years. I currently own an '04 R1150RS, '90 K75S, and '76 R90S, yes I have one of each model! I was getting my oilhead ready for spring yesterday and changed the oil including gear box and rear end. The bike has 35,000 miles on it and I have used synthetic gear oil since it was new. I bought some AMSOIL 75W-90 synthetic and changed the oil in both the gearbox and rear end. I just noticed that what I put in is an API GL-4 rated and the owner's manual says use an API GL-5. I have done some research on google but can't really tell if the GL-4 is OK to use or not. Anybody out there know anything about this? Will my transmission self destruct if I leave it in or will it be OK? I usually go about 25,000 miles between gear oil changes when using synthetic.

[r11rs94]

Hi, name's Dick and I am new to this forum but have ridden BMWs for way over 30 years. I currently own an '04 R1150RS, '90 K75S, and '76 R90S, yes I have one of each model! I was getting my oilhead ready for spring yesterday and changed the oil including gear box and rear end. The bike has 35,000 miles on it and I have used synthetic gear oil since it was new. I bought some AMSOIL 75W-90 synthetic and changed the oil in both the gearbox and rear end. I just noticed that what I put in is an API GL-4 rated and the owner's manual says use an API GL-5. I have done some research on google but can't really tell if the GL-4 is OK to use or not. Anybody out there know anything about this? Will my transmission self destruct if I leave it in or will it be OK? I usually go about 25,000 miles between gear oil changes when using synthetic.

First welcome aboard, I just pick up my gear oil Yesterday. I use the API GL-5. I just stick to the BMW oils. I know they cost more and are proberly no better, but thats me. I do no others that used the GL-4 with no problems. But stick around I'm sure some one with more experience with synthetics will post soon. good riding to you.:thumb

[BubbaZanetti]

most of the high milage, long time bmw experts round here recommend NON-synthetic, GL-5 single weight or 80/90 weight oil (specifically Castrol Hypoy-C). i've been using it in my final drive for a few years now. transmission opinion seems more up in the air. to be honest, i'm not sure what i'm running in that right now, maybe a synthetic 80/90 but many use the castrol there too.

try the search function and do some reading, lots of informed viewpoints there.

[BuddingGeezer]

GL5 oil has 2X the extreme pressure additives as GL4. GL4 is used mainly were brass or bronze (yellow metal) is used in the gears. Many auto transmissions use GL4. The EP additives are somewhat corrosive to yellow metal. I would not use GL4 oil where GL5 is called for.

I had this problem in reverse. I have a Yamaha outboard and the lower unit calls for GL4 and most of the lower unit oil I could find was GL5. After much study I found out the difference and I bit the bullet and bought the GL4 Yamalube. I don'y know what a new 90 HP motor costs but I bet it's a bunch.

Ralph Sims

[glennhendricks]

I'd change it out but it took the Navy 4 years to beat that into my head. Actually just A school.

I always run the recommended weights and or specs on all my vehicles. I figure they know what they're recommending.

[Ridealot]

Hi, name's Dick and I am new to this forum but have ridden BMWs for way over 30 years. .


I personnally know Dick. And he ain't kidding, its way way over 30 years. :stick

Welcome to the party Dick.

[climbersteen]

It looks like I'll be a'changin this gear oil to GL-5. Thanks for all the input. And thanks Tom for the endorsement, I did say over 30 years and it's all been great!

[Hottech]

While your on the subject of gear oil does anyone have any information on what a SP-1C rating stands for. I can buy a case of 80W-90 gear oil with a SP-1C rating but have no idea what that means.

[Tazerbarb]

Howdy - another newbie here.

I just bought my first BMW, an '03 R1150RT with 34K miles. I had the 36K service done this week, so I know I'm good to go for a while. I am used to doing routine maintenance on my machines such as oil, plugs, brakes, etc. (Previous bikes were all Japanese makes). I never had a problem switching to synthetic oils on bikes that had traditionally used non-synthetic. My question is this: has anyone experienced any problems with seals or gaskets switching to synthetics when having 30K-plus miles on your machines?