Moto Grand Prix
Main Motorcycle: 03 TBird
Join Date: Apr 2004
Location: Nutmeg State
Other Motorcycle: '76 Bonnie
Fork Oil Research
In trying to translate my '76 T140 owners manual recommendations on fork oil to current products, I thought I share the information found. Hopefully the extrapolations of the information are correct.
The owner's manual lists several specific AFT oils, a couple being Mobil ATF 210 and Castrol T.Q.F.
Information is still available on both these products which are type "F" or Ford spec trans oils. One opinion expressed was that Type F was basically a 20 weight motor oil base with additives and red dye and without friction modifiers.
The specs found on Mobil ATF 210 were: 8.5 viscosity @ 100 degrees C, 39 viscosity @ 40 C., Visc Index 196.
The Castrol TQF specs were 8.5 viscosity @ 100 degrees C, viscosity @ 40 C not listed, Visc Index 166.
The two products were similar except in the VI, which apparently indicates variability of viscosity within a temperature range, higher number being less variability.
One product that seems it may match up is Maxima Racing Fork oil in 15 weight which has 8.5 viscosity @ 100 C, VI 151.
The Maxima regular 15 weight fork oil also has a 8.5 viscosity @ 100 C and 47 @ 40 C, VI 151.
These look similar to the original ATFs seeming to indicate that a 15 weight fork oil may be in the general ball park of the original specs.
I didn't look into other brands but hopefully similar information is available.
That being said, one thing learned was that oil grade (weight, a misnomer?) is Not it's viscosity. A local dealer thought that 7 1/2 weight fork oil was about equal to AFT but it doesn't look that way from the comparisons above
To take the weight out of the picture, there are also a couple current synthetic ATFs, Amsoil and Redline, that are noted as "Racing" and referred to as type "F".
The Amsoil is listed as 7.1 viscosity @ 100C and 40 @ 40C.
The Redline is listed as 10 viscosity @ 100C and 54 @ 40C, a bit higher than the former.
To me it looks like a 15 weight fork oil, or perhaps a mix of 15 and 10wts may be a reasonable match to the ATF specified in the T140 manual, with the Amsoil Racing ATF an alternative.
Any supporting or contradictory information would be welcome.
Last edited by Beemie; 05-25-2015 at 01:38 AM.