There is an article on this website on actual viscosity and viscosity index values for oils here is the link again, (it also has other oil information). The viscosity index of an oil is simply how fast or how slow, with temperature rise and fall, the oil thickness changes. One needs to THINK about how viscosity changes with heat (not just atmospheric, but the heat produced by considerably bumpy terrain, which affects viscosity, some less or more than others). However, a good argument can be made that in some circumstances. UNDER NO CIRCUMSTANCES CHANGE OIL VISCOSITY TO COMPENSATE FOR FAILURE TO REMOVE AS MUCH STICTION IN THE FORKS AS POSSIBLE!Ī medium-high viscosity index is generally a good thing for most riders for fork oils. NEVER higher than SAE 10 for the non-GS models (some GS models specify use of different oils, SAE 10 and SAE 15, in right & left fork legs, respectfully). Only in the instance of heavy to very heavy loads (rider & passenger weights & luggage), or very aggressive performance, is an oil heavier than an actual SAE 7.5 weight of any benefit. USE MY CHARTED INFORMATION in that above LINK, for oil viscosity information!Įxcept for some GS models, all the BMW's (that this article applies to) need a rather thin oil, approximately SAE 4 (like that military oil, as above), so do not willy-nilly change the viscosity grade to much higher. & with the information in the following article on this site:ĭO NOT DEPEND ON MANUFACTURER'S SAE NUMBERS. You can use those two viscosities, 4.9 Cst and 13.2 Cst, to compare (perhaps!), with other manufacturer's oils specs. too cold to bother about for motorcyclists (unless very crazy about cold weather riding!). MINimum 4.9 Cst at 100° C (generally accepted as same as 210☏). To save you the trouble of finding the information, just the viscosity specifications for that oil are: Oil with a "5606" military specification can be depended-upon for viscosity (but not for some things you really want for your fork oil).
#FORK OIL VISCOSITY CHART FULL#
That oil was actually a military hydraulic oil, you could find its full specifications using a search engine for: MIL-H-5606- (probably -E now). Because of these various things, and other reasons I won't bother to get into, I highly recommend you stay with one manufacturer, this is particularly so if you are trying different viscosity grades.īack in early Airhead & K bikes days, the oil BMW used was "BMW red fork oil". Viscosity measurements & temperatures are more accurate between manufacturer's for engine & gear oils not so, apparently, for many suspension & fork oils. For fork oils & suspension fluids, the various manufacturer's do not agree on measuring viscosity sometimes they don't do more than give some sort of approximate SAE grade value. especially the full synthetic or part synthetic fork oils. Due to how specified, & lack of stiction fighters & other characteristics, you are better off with a real fork oil like Spectro's. They are of good quality, have low stiction, wide temperature range (excellent viscosity index), & the viscosities can be depended upon.
I prefer Spectro's fork oils and suspension fluids. This article applies to Pre-Airheads, Airheads, Classic K bikesĭiscussion of oil types and characteristics: The following section should be used with: Snowbum's BMW Motorcycle Repair & Information WebsiteĬlicking on them at every visit helps support this website!Ĭlicking on something inside an advertisement helps even more!Īlso, thanks for the donations! The donating link has history andįront Fork Oil discussion filling amounts hints.
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