I am fast approaching by 1000 Mile service, on my 2018 Milwaukee eight. I have always ran synthetic in my twin cam. But my dealership is suggesting running regular Harley Oil instead of any synthetic. Their logic behind this, is that since the milwaukee-eight holds close to 5 quarts of oil, and has an oil cooler it is not necessary to run synthetic. However since it's a 114 the manual does suggest synthetic in the transmission. I'm just wondering what other people are doing. I am NOT looking for oil brand suggestions, if I use synthetic it will be Mobil 1 V-Twin oil. I have used it in my twin cam and Sportster Motors with great success. I'm just looking for opinions on synthetic versus standard oil in the Milwaukee eight. Thanks

 

Your dealership is right but probably has too much conventional oil in inventory and has to move it. If they had too much synthetic, they would be recommending that. Your manual is also right. Run what ever you want.

 

SYnthetic. It’s a far superior product over conventional

Redline 20w-50 FTW

 

I use HD Syn3 and HD Formula+ in the Trans and Primary. I had the 1000 mile service completed at the dealership and did the 5000 service myself. I'll change all three holes every 5000 miles. My M8 runs great, no sumping or migration so I ain't changing anything.

No matter what you use. Just change as scheduled.

 

It does not really madder. SYN stands up to heat better in the long run. Oil cooled heads , liquid cooled they still crank out some heat.
I run M1 20/50 Only because locally it is priced right and works in all bikes

 

I been runnnig M1 15-50 from Walmart $19.99 for 5 Qt jug in my bikes for over 15 years for many many miles . No garage queens here .
And now both sons are also riding and using the same . I tell them both CHECKING and CHANGING the oil is one of the most important things to do to their bikes or cars . And the easiest things to do !

 

Ohio as far as I know all 114's come out with SYN 3 standard at point of sale.

 

Strange how dealers vary. At my 1000 mile service the dealer used Syn3 oil and Formula+ in trans and primary. At 5000 miles I sent a sample to Blackstone Labs via USPS. Unfortunately, they never received it, I've been using them for years and never had an issue. Our mail service is horrible here. Was anxious for the results.

 

Use what your onwers manual tells you all M8s are shipped using SYN3 ??? Leave that dealer there just pushing out there overflow

 

The advantage synthetic has is it maintains it's properties over a longer period of time and resists breakdown at high temperatures better. In an air cooled engine that can overheat synthetic should be better and you won't need to change your oil as frequently. The dealer wants to sell you HD brand oil which has a huge markup. You can probably find a good synthetic at the same price.