Oil and Oil Filter- which one should I use?

[wayne]

Here's the simple answer- Castrol GTX 20-50 (Suzuki's RE Oil was a 10W-20W-50 oil). Images and/or information provided by members from each named region.

It's cheap, it's readily available, it's tried and true and actually recommended by the Suzuki Factory. Castrol even took out ads touting they'd been selected as a suitable oil for the RE5. There are many modern oils that may be better (or maybe not). When you run up 100,000 miles on one of these new oils, let me know, I'll update the post.

Use GTX in the engine sump and the under seat metering oil tank. For the gearbox/transmission, some people use straight 80 w gear oils and this seems to help if you're having starter clutch problems or otherwise, any motorcycle oil for wet clutch gearboxes in the 20 to 40W range. GTX should not be used in the gearbox. This is the brochure that comes with US GTX in 2021. AU was the same 35 years ago re wet clutches. I'd imagine this applies worldwide:



If you want to give it a go, Castrol Technical have recommended Castrol Power 1 Racing 2T. It's an esther and has low ash. A new member WIZNORTON who has extensive rotary racing experience (albeit not with RE5's) made an interesting point (his post is further down). On the plus side, Two stroke oils are formulated with the fact in mind they will eventually become an aerosol to be carried in the intake. Sump oils, like GTX, are not. On the downside, changing the viscosity of the oil recommended may affect mixture (albeit in a small way). Food for thought.

Oil Filters:

NB: The original filter has a bypass valve and this has been misinterpreted on some forums as a non-return valve. They are not the same thing. Just a technicality, you can live without either or with one or even both. Read the post by HUDSON below re the non return valve. Sounds like a feature worth having.

A Suzuki option is part #16510-05A00. Member KANONKOPDRINKER remembers this advice from Sam Costanzo himself. David (the member) has been using these without any problem for years. Sam told him the only thing they didn’t have was the emergency by-pass valve.

US From Bill L on Facebook: Sam Costanzo, the original owner of Rotary Recycle, used to recommend Fram PH2951. In particular, I recall him saying its bypass valve pressure (12 psi) was closest to that of the Suzuki filter (I don't know its precise spec). Lots of people are not fans of Fram, so cross references to that include Wix 51394 (8-11 psi); Fleetguard LF3614 (unknown); and in Australia, Ryco Z158 (unknown) EDIT: I don't think the Z158 is available any more but see below for AU.

They are black, against the O.E. silver.

From Michael D Callahan on FB, apparently the Suzuki Samurai and Geo Tracker are the same filter (as the RE5).


Other options are: AU/NZ Ryco Z386 (has the bypass), the following may or may not: UK Royal Purple 10-2840, USA Toyota Corolla short can part no. 90915 03001, K&N HP-1003

In the UK from member T140V the Mobil 1 M1-103 filter works.

In the EU, members Ronald Bakker and Pete Assmann use this. It has an additional feature. This one has a non-return valve which has some benefits (faster to reach pressure from a cold start):








AU:



EU:

From Michel Stoelen, Member TYP110, one of our RE5 engine rebuilders. Michel has checked with Castrol Belgium and they have confirmed that GTX 20-50 is not available in Europe. For the RE5, they recommend Castrol Power 1 4T 20-50w. Michel has questioned them about the ash content and it's 1.2% vs original GTX at 0.98%. Very close, a low ash oil, that's the important bit.

Filter in the EU same as above:



NZ:




USA:




or




UK:




An example of a straight gear oil for the transmission (US market packaging):

[wayne]

Above was the simple answer. Do that and you won't go wrong. Here's a bit more information:

Suzuki Service Bulletin #2-

".....approved oils for use in the sump and metering pump oil tank are: Shell Super X 10W 20W-50 Motor Oil and Suzuki Rotary Engine Motor Oil".

Suzuki Service Bulletin #11-

"......U.S. Suzuki is now also recommending Mobil Super Motor Oil 10W-40 as an acceptable oil for use in the RE5."


We have a US member who is a factory trained mechanic and has done the 100,000 trouble free miles (several times over on more than one bike and proper units). The Shell and Mobil oils below are still available. Good luck finding the oil on the right of the pic. He makes the following comments (note GTX ash is currently 0.98%).

"I made a note back in the day that the Shell ash was 0.65. Like Tom93 has said in prior posts, the chemical makeup

probably changed many times especially when all manufacturers went to the slippery fuel efficient additives , to improve gas mileages, in the oils.

My notes from service school, Suzuki was looking for a "low burning point"."






In Europe, our engine rebuilder has his own choice:

Michel is an experienced rebuilder and services the RO80, W2000 and RE5 engines. He personally uses Fuchs Titan Syn MC 10W40.

[timpa136]

I need to post a correction of sorts. I have been using the Mobil 10-40 in my bikes

but now I have confirmed by Mobil that the 10W-40 Super is now semi-synthetic

and is unfortunately no longer recommended .Luckily I have a supply for a few miles to go.

I will go to with Shell  Formula 10W-40. I did use Shell 5W-20 in my RX8 and no problems.








Tim

[hudson]

While we are having some fun with the never ending oil thread, thought I would add my two cents.

    

This is the Suzuki Transmission oil that is mentioned in the RE service manual. This went in every Suzuki trans at the dealership where I was employed in the 1970's until it was discontinued sometime in the late 70's. When Suzuki introduce their Four stroke GS series (1977 GS 750 ) we started to carry Castrol GTX in bulk for our service department to use in the four strokes. I remember there was a discussion with the Castrol Rep. about Zinc levels for protection of the trans and we switch to GTX for all transmission services. I have learned more about the " zinc " in resent years from my 20 years of involvement in motorcycle drag racing.

The zinc we referred to was actually "Zinc dialkyl dithiophosphate" ZDDP as it is often referred to now, was an additive that began use in the 1940's. It was the miracle wear protector additive as it would bond to metal surfaces and provide protection on sliding metal surfaces such as cams with flat tappets and is very beneficial in gearboxes also. In the U.S. sometime in the early 1990's or there about our Environmental Protection Agency , EPA started to restrict and greatly reduce the amount of ZDDP in our motor oil as it was determined to coat the inner workings of the catalytic converters and render them inoperable if the engine was consuming its crankcase oil. I do use GTX 10-40 in my RE trans. ( 20-50 will make the starter clutch slip when the engine and oil are cold ) I always add some ZDDP as I believe it does add protection to the primary chain, starter clutch and gears. I also think it is beneficial in the sump as well to protect the eccentric gears. I am running GTX 20-50 in the sump and injection.

There is an abundance of information and sources of ZDDP on the internet. A small 2 oz. bottle will treat 5 quarts and can be had for a few bucks.



Brian

[timpa136]

    As an alternate to the Suzuki transmission Oil Suzuki says 20W/40 motor oil.

I have not used this but always thought that that weight rating usually was a Diesel rated weight classification.

I would expect there are different additives for the Diesel fuel contamination but more

importantly, an additional anti-wear additive that a gas catalytic converter vehicle could

not use as poisoning of the catalytic convertor would occur.

Tim

[wayne]

I've heard of the use of Castrol R (basically a modified Castor Oil), not for the sump, but to replace the under seat (metering oil). It can be used as a premix and some claim wonderful properties for it including the fact it was so good they used it in old military aircraft etc. I've seen photos of an RE5 using this and its exhaust looked very clean.

Please do your own research, this is what I gleaned from my own searches and my conversation with Castrol Technical:

A bit of 'net research gave dubious results. It is true Castor Oil was used in old fighter aircraft etc but because it was the best at the time.

So onto Castrol Technical and the use of this oil in Rotary engines. We had an extensive conversation.

Castrol R contains no detergent and is therefore very low ash. Exactly how low he couldn't tell me but said he could get back to me. It's more commonly used in racing.

However, and here's the kicker in my opinion. It leaves a gum residue. Not a problem for racing where engines are regularly rebuilt and high heat can help to burn some of it off. However, he said that it would not be recommended for cruising around on a street machine.

Compared to modern synthetics, he said that Castrol R copes well with high temps but would be "shockingly bad" from a residue point of view. He personally felt it would be a "last resort". He also warned it should not be used in a metering system, premix only (as I've heard used in an RE5).

Unlike pure Castor oil, Castrol R has additives which make it reliably miscible with fuel. So that's not an issue while pure castor will separate.

He felt pure synthetics would be the best option. Regular Castrol synthetic 2 stroke has a 1% ash content. Lower even than the Castrol GTX now supplied in the EU. He noted that Marine 2 stroke is almost completely ashless (but I think that was based on the lower overall operating temps so wouldn't be the same result in a rotary).

His recommendation, Fully synthetic ester like Power 1 Racing 2T. It has the cleanest burn of all their oils.

So if you're thinking of using Castrol R, be warned. It is low ash, but leaves gum and is not recommended by Castrol Technical for a rotary engine. Try the synthetic 2T if you wish. Sounds good but for me, the cheap, readily available and proven track record of GTX still wins the day.

[wiznorton]

Sorry if this has been explained at length elsewhere, (I have done a quick forum search and not found an answer I'm afraid)

But what (if any) is the objection to using 2T injector oil in the under-seat tank? At the end of the day it is being pumped into the combustion area to lubricate the apex and side seals. Multigrade engine oils are not primarily designed to be burnt, and although the ash residues quoted in this thread are quite low, that are still significant compared to a purpose made 2T oil.

I realise that the sump oil is doing a different job in the Suzuki, but in our Norton and Hercules engines I wouldn't think of using a multigrade, even though the oil also has to lubricate the rotor and main bearings. It strikes me that using the same oil in the sump and metering pump on the Suzuki doesn't make much sense as they are doing two very different jobs.

I await to be shot down in flames!!!!!!

[wayne]

Look at the post immediately above yours where I talk about Castrol R. Near the end I note that Castrol Tech says that Power 1 Racing 2T would be a suitable oil.

For most of us though, it's boils down to this. GTX is cheap, readily available and recommended by the factory. It does the job and has been very successful in keeping us all on the road. It's very possible that there are superior oils. For me, 2T's long term effects are entirely unknown. Might be fine. But I don't need to find out.

From Castrol Tech, they think that particular two stroke should be fine. Go ahead and try it. It was Castrol themselves talking. Note also that the post above was inspired by someone running Castrol R. I'm open to new ideas. But read Castrol Technical's response to that oil.

What do you guys race your Norton's on?

[wiznorton]

Hi Wayne, thanks again & sorry for making you duplicate your previous comments, and I take your points on board about being tried & tested. My real reason for raising this was because of the two very different roles for the lubricant in the Suzuki application. I find it difficult to grasp that one type of oil should be used in both sump and metered pump.  How much carbon buildup do you tend to see on a 10,000 mile engine on GTX?

In the Nortons we currently us Silkolene Classic 2T both as a premix and core cooling / rotor and shaft bearing lubricant carried in the air stream. (which is then drawn unburnt into the ejector venturi in the exhaust ) I don't know how available this product is globally though.  www.silkolene.com/motorcycle/classic-oils/classic-2t-premix/

My other thinking for using a 2T oil in the  Suzuki is that it is designed to be carried in the fuel air mix, which a multi grade is not.

In our aircooled engines, we see core cooling air temperatures over 150 degrees C as it exits the engine and at this temperature the Silkolene oil is right at the limits of its' thermal range.

I have looked at using Mobil Jet Oil 2 in that application as it is specified for use to just over 300 degrees in aircraft engines (so you have to believe that data as it's very highly regulated ) I have discussed this with Mobil and they are totally unwilling to offer any advice for this application as it is not a design parameter for that oil.  www.exxonmobil.com/en/aviation/products-and-services/products/mobil-jet-oil-ii

For that reason, I'm also slightly surprised that a Castrol technician was prepared to stick his neck out and recommend an oil which hasn't been tested in a particular application. Good for him!  Did he add any caveats to his advice?

And finally, from my observations of the complexity of the Suzuki carb, I can only assume the RE5 is very sensitive to fuel / air ratios, and as such I would guess that changing to a different viscosity oil might possibly affect the mixture (albeit very minimally)  and create some problems

[wayne]

No apologies necessary. Enjoyed reading your post above. Very good to have some input from a different angle particularly because it's empirically based.

I take your point about design with respect to how the oil is carried, ie in the airborne mix. Totally different to a multi grade engine oil.

My only concern which I should have broached with the Tech was temperatures. I know Rotaries run considerably hotter but I don't have any figures. I think I need to do some research about internal temps and find out the temperature ranges for these 2T oils. Thing is though, why would GTX be any better from that viewpoint? And I'd imagine, if nothing else, garden variety 2T oils would be more temperature tolerant than a typical sump oil because they must directly tolerate some of the combustion process.

The Tech had no caveats about that oil.

Please feel free to contribute and question. I collate suggestions, experience and ideas into these "quickie" guides but the book's not closed.

[timpa136]

Interestingly I just got back from my new favorite loop ride and in one Rural area an ATV went past on the road and

he was burning caster based or Blendzall.

Notes say Exhaust temperatures of the RE5 14-1600 degrees F. , with a maximum temp of 1900 degrees Yeow.

Not sure of the oil temp in the rotor.

EDIT:  From my own note on a post elsewhere, Rotor Temperature

as high as 266 Degrees Fahrenheit

Tim

[wayne]

I've always heard 3 to 400 degrees hotter than a 4 stroke but never knew what the actual temps were. That marries well with a bit of Google research on four stroke temps. The most consistent answers seem to be between 750 to 1100 deg F.

[timpa136]

New packaging for the US?

EDIT: This is your Father's motor oil.



*NOT FOR USE IN MODERN ENGINES WITH CATALYTIC CONVERTERS OR WET CLUTCH APPLICATIONS
Specifications:

API SJ

[wayne]

Thanks Tim. Main post updated with what looks like USA's new packaging.

[hudson]

  Tim thanks for the post with new GTX bottle. I noticed the label mentions high Zinc content. I'm hoping this means their "Classic" has more zinc than their standard blend. I searched for the classic blend GTX a couple of years ago and thought it wasn't available in the U.S.

  I also noticed in the filter video that the filter is stamped 3/4 that must refer to the tread size. When I did my restoration I realized the filter is 3/4 with 16 threads per inch ( standard 3/4 fine thread here in the U.S.) Odd that a Japaneses/metric motorcycle has inch threads.  The RE also has some other components that are in inch dimensions rather than metric.
  The gentleman in the video mentions the "Non Return Valve" I have always referred to it as an " Anti Drain Back Valve" which is to prevent the system from siphoning the the oil cooler and lines, filter and oil passages back to the sump resulting in a dry start up after sitting. He is right that it's an important feature when looking for replacement filters. I am still using and able to get O.E.M filters from my local Suzuki dealer although they are expensive.

Regards, Brian