Yamaha TRX850 Enthusiasts Forum

Is it a good idea to use synthetic or semi-synthetic oil in TRX engines?

Penrite full synthetic works well with mine. No clutch slip either. The engine and gear shifts are smoother too.

Semi-sync is generally recommended for "older" bikes... But I guess it doesn't really matter considering the average oil consumption of a TRX and how frequent oil changes should be!

I vouch for the Penrite full synthetic too. It was actually my second choice when I found the local retailer wasn't stocking the Shell Advance blend anymore.

The Penrite' is 15W-50 but it seems less viscous and clearer than the 10-40 Valvoline I used to run it in (and Penrite claim it replaces 10W-40).
It certainly runs nicely and I'm sure more quietly, than with previous oils. I've yet to run enough hard miles to check whether the engine consumes it quicker or not. (Before the rebuild it drank Motul race oil like beer at a bucks night! But that's another story.)

A good quality oil replaced often is more important than fancy oil A or B, especially if your Rex is a drinker.
Use a reputable brand semi and change it often. Motul, Belray, Motorex, Shell, Castrol just to name a few.
No use chewing up $$$ of full synthetic on a standard motor.
If you have done extensive engine work then maybe different consideration could have merit.

Thanks all for the replies.

I was a bit unsure about using anything but normal mineral, but on the strength of the comments I have opted for semi-synthetic 5w-30. The engine is a bit of an unknown quantity because I took it out of a crashed bike which no longer had it's speedo. So I really have no idea how many miles it's done. It sounds ok but I've only run it in the garage so far after the bike rebuild. If I rev it hard there is a bit of smoke, but it's been standing a long time so I guess you might expect this. I'll have to see what it's like when I get it re-registered and back on the road. Nearly there.

Standard grade is 15W/40. Why would you go to 5W/30????

Standard grade is 15W/40. Why would you go to 5W/30????

Simple and honest answer is that when I was in the shop my memory told me the specification was for 10W-30, which they didn't have, so I bought 5W/30, which seemed reasonable to me, nor knowing much about oils.

But, Silver, your question made me think a bit and wonder if it matters, so I've done a bit of superficial reading on the subject. There's mountains of highly technical stuff out there and I've only skimmed the surface, but on the basis of it I'll lob in a few statements to see if anyone has any major disagreements.

• 1. According to my TRX handbook, there is no single standard grade; they range from 10W/30 to 20W/50 depending on ambient temperature range.
  
  2. The W rating is only of any interest on start-up at low temperatures. Since I do sometimes use my bikes at temperatures down near zero, for the few seconds of really cold running 5W migh actually be an advantage?
  
  3. In theory, a 10W/40 should give better protection at running temperature than the 5W/30 because of the higher viscosity up near 100 degrees. However, (and here I'm on really shaky ground) as I understand it multigrade oils use something called V1 additives to reduce thining at high temperatures; the greater the viscosity range (e.g. 10W/40 Vs 10w/30) the more additives are used. Apparently, there is a problem in that these additives can 'shear' or break down at high temperature, especially as the oil ages, so the less there are in the first place (as in 30 rather than 40) the better - provided the oil still has sufficient viscosity for the particular engine. Is this right?
  
  4. If so, in the 16 years or so since Yamaha specified 10W/40 is it reasonable to assume that the additives have improved so that todays 5W/30 might actually retain a higher viscosity and better protection at running temperature than the 10W/40s of the day?

Just wondering. Maybe I should get out more

sound convincing. Good luck!

Planx wrote:

Standard grade is 15W/40. Why would you go to 5W/30????

Simple and honest answer is that when I was in the shop my memory told me the specification was for 10W-30, which they didn't have, so I bought 5W/30, which seemed reasonable to me, nor knowing much about oils.

But, Silver, your question made me think a bit and wonder if it matters, so I've done a bit of superficial reading on the subject. There's mountains of highly technical stuff out there and I've only skimmed the surface, but on the basis of it I'll lob in a few statements to see if anyone has any major disagreements.

• 1. According to my TRX handbook, there is no single standard grade; they range from 10W/30 to 20W/50 depending on ambient temperature range.
  
  2. The W rating is only of any interest on start-up at low temperatures. Since I do sometimes use my bikes at temperatures down near zero, for the few seconds of really cold running 5W migh actually be an advantage?
  
  3. In theory, a 10W/40 should give better protection at running temperature than the 5W/30 because of the higher viscosity up near 100 degrees. However, (and here I'm on really shaky ground) as I understand it multigrade oils use something called V1 additives to reduce thining at high temperatures; the greater the viscosity range (e.g. 10W/40 Vs 10w/30) the more additives are used. Apparently, there is a problem in that these additives can 'shear' or break down at high temperature, especially as the oil ages, so the less there are in the first place (as in 30 rather than 40) the better - provided the oil still has sufficient viscosity for the particular engine. Is this right?
  
  4. If so, in the 16 years or so since Yamaha specified 10W/40 is it reasonable to assume that the additives have improved so that todays 5W/30 might actually retain a higher viscosity and better protection at running temperature than the 10W/40s of the day?

Just wondering. Maybe I should get out more

Oils may have changed, but you are still using the engine that Mr Yamaha made back then. Modern 5W/30 oils won't give your engine better protection, they are designed to help with emissions regulations for newer vehicles with more modern and higher tech engines.
I would wouldn't use anything less than a 10W/40, but it's your motor so your call.

2 cents worth:
Trying Silkolene Super 4. (semi synthetic)
If it is good for the latest Yamaha superbikes, it should be good for a TRX as well.

My goal is to see if I can get better shifting on the track with this oil.

I use Motul 5100 in mine and it has 73000km on it and uses no oil to speak of.