I have poured over the last six months worth of debates on these oils but have yet to figure out the difference of the two mobil and the Motul oils.

I am not sure how much the MX4T is but at AutoZone, the Mobil 1 was $4.49/quart. My current oil, Motul 5100 is running me about $23 OTD for a gallon. This would be a savings of $4 per gallon and I am wondering if it is nessessary to run the higher dollar MC oil in my RFS if there is an equivelant oil on the market, due to the reports of clutch slippage or intermittent "fade" of the hydro clutch.

My understanding is that the mx4t contains zinc and doesn't contain friction modifiers that are in the newer auto oils. These friction modifiers can cause clutch slippage. Also the motorcycle oils contain more phosphorous and zinc (car oils can't have these due to effect on catalytic converter). The phosphorous and zinc provide smoother shifting and protection under high loads.

Remove the mobil1 15w50 car oil from your list and use the mobil-1 mx4t 10W40 in it's place. Cost is around $7.50 a quart at autozone.

If low cost is your main criteria -> One of the best conventional oils that is suitable for use in a four stroke motorcycle is chevron delo 400 - they sell it by the gallon at costco - I believe they stock 15W40.

jeff
'01 gasgas ec300

The Chevron Delo 400 is a diesel engine oil from a hydrocracked crude oil base stock. What's that mean? Diesel oil is designed to suspend contaminants well so that they can be transported to the filter. Hydrocracked oil comes from the same base stock and conventionally refinded oils it just has more of the impurities removed using the hydrocracking process which Chevron developed. Personally with the limited volume of oil the RFS engines have I would use nothing but a top line synthetic of either PAO or Ester base (some hydrocracked oils are labeled "synthetic"). Mobil, Amsoil, Motul and a few others make a great true synthetic that will provide maximum protection. Worry about the clutch slippage if it actually happens not based upon speculation that it could because chances are VERY high you won't see it.

Both mobil and chevron discourage the use of their newer synthetic auto oils in motorcycles due to the addition of friction modifiers (check out the faqs on their websites). Whether or not you believe this - the increased levels of zinc and phosphorous that are added to the motorcycle specific synthetic oils are beneficial additives for a 4 stroke motorcycle oil to have.

As far as the delo-400 is concerned - just because it's good in a diesel, does that mean it's bad in a motorcycle? Chevron recommends it for use in motorcycles over their new synthetic - it has a relatively high phosphorous and zinc content which are good additives to have in our application.

I agree with your argument - I use the very best oils that I can and change them very often - the additional cost is pretty cheap insurance. From what I have read (on the oil companies webistes - not elsewhere on the internet) mobil-1 motorcycle oil is superior to the mobil-1 car oil for use in a high performance motorcycle.

jeff
'01 gasgas ec300
'95 honda xr300r

I think oil selection for the crankcase of a 2T is less critical than a 4T since in the 4T the oil is a lubricant for the entire engine. I'm sure the Delo would work but how well? Would it be considered an equal replacement if the bike were to experience a failure under warranty? Engines with turbos have a problem with oils "coking" if the turbo is not given time to cool of with the oil circulating. This problem is typically seen in organic lubricants and is typically not an issue with PAO or Ester based synthetics. Given that the RFS does not have a turbo BUT does have a tiny oil volume the thermal breakdown of the oil should be a top priority. Suck up the cost difference and stick with the Motul or go with the MX4T and leave the diesel lube for 2T bikes and diesel trucks.