I have an 05 softail twin cam 88, my next oil change i want run all synthetic, can i use Mobil 20-50 in all 3 holes? Motor, trans and primary?
Thanks!

 

Might as well be the first to ask, why would you want to put motor oil in the transmission????

 

There has been many threads and lots of opinions on using one fluid in all 3 holes and I think the only possible benefit for doing so is convenience, you're only stocking one fluid but there are much better choices available. My opinion is transmissions need a proper gear oil, the idea of putting engine oil in a transmission doesn't sit well with me and many others.

Redline transmission oil or Mobil 1 synthetic gear lube are much better options as are many others. I discovered Mobil 1 V-Twin 20W-50 in the primary caused clutch slippage, it's not JASO rated but I've had great success with Mobil 1 Racing 4T 10W-40 synthetic in the primary which is JASO. I found the Mobil 1 V-Twin in the engine increased top end noise substantially but LiquiMoly 10W-60 synthetic is the quietest of all the synthetics I've tried.

I'm running all synthetics but I'm a big believer in the right tool for the job

 

Lots of people run the 20w50 in all three holes with good results. I'm one of those who believe it's better to run a gear oil in the trans. Harleys primary oil was in the 10w40 range from what I hear. I run Mobil 1 20w50 in the motor, their Racing 4T 10w40 in the primary (JASO approved) and BelRay 85/140 hypoid in the trans. Lots use the Mobil 1 75/140 gear oil in the trans. All the Mobil products are available at the local Walmart.There are tons of oil threads with various opinions.

 

Or Mobil 15W-50 in the motor too. And the cheapest dino based 10W-40 or 20W-50 (Wal-Mart Tech for me,) in the primary. Don't waste your money. (154,000 miles currently.)

 

Viscosity wise, the 20W50 motor oil is about equal to 80W90 gear oil, as shown on the chart below. Additive package wise, they are different as they are meant for different environments. You can, and a lot of folks do use motor oil in the tranny and don't seem to have any issues. I choose to use gear oil in mine. Changed at 15 to 20K miles thats 5 or 6 quarts of gear oil over 100K miles. Not a big deal in my opinion.

It's your tranny, money, and choice.

 

I was asking because the dealer told me i can run the syn3 in all 3, just figured if i could run their brand, why not Mobil-1

 

I use Mobil 1 20-50 in my S&S engine, as that is what they recommend and am installing a Baker trans with the stuff they recommend, Spectro HD 6-speed, plus H-D primary oil. It is so easy to get the recommended stuff these days, log on, pay, delivered to your door. Simples! I can't see any benefit in playing around.......

 

This is a good read from Baker on their thoughts in regards to transmission lubrication: http://bakerdrivetrain.com/wordpress...ders-Baker.pdf

 

Good article! I wonder if Baker Would actually recommend a specific trany lube?