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JJ,
It’s the VP RS-7 that seemed to develop problems after it was reformulated (see Doug’s prior note). We had a lower end failure for no good reason using it two seasons ago at GJMS, and the next race another person reported a similar failure at Bandi. It was then that I heard of other failures, at the national level. That’s why Rotax changed to the Motul oil this year (they actually dropped the RS-7 in 2005 and spec’d Motorex oil, which also seems very good, but is very difficult to find and even pricier than the others). I’ve heard of no problems related to the Motul, other than that it tends to separately a bit more easily and thus the fuel should be well-shaken before use.
Now understand that lots of people have been using RS-7 without problems, so it’s not a guaranteed road to engine failure by any means. But there have been enough problems reported that I don’t see any reason to stick with it. Curt has a point about sponsorship, but I’ve not heard any stories of the VP distributors lavishing cash on the series. (Maybe they have and I just don’t know about it….)
There was a problem with VP oil 3 or 4 years ago and it was only a small amount of one batch that was contaminated with motor oil in the bottling plant. They have corrected that one time problem years ago. RS-7 is a very high quality 2-cycle synthetic. It is not hard to find, we have it instock always.
I’m sure lots of companies can make a good synthetic, or synthetic blends. The best fuels for R/C pylon racing are a blend of syn and castor, just in case you get too lean. Castor works great too, but it foams and does tend to varnish more which can reduce engine life unless you like to tear down and clean your engine often (which I’m sure some people do).
Can the folks who had problems confirm that this was 3+years ago as Blink states. If so then this could very well have been a one time problem.
Again, I’d really like to know what Synthetic or Syn Blend I can run and stay in spec. It sounds like RS7 is the current spec, but if the Rotax owners need to run Motul to maintain their warranties then I think we should take that into consideration.
JJ-
In my case, it was the first race of the 2005 season at GJMS. The other person who described a similar experience was the following race at Bandi. I’ve not heard of problems since then on the Rotax boards, but that’s probably because Rotax changed oils.
Last season we ran Motul for Rotax Max Challenge races (as spec’d by the RMC) and VP RS-7 for CSC races. (So aside from protection issues, it’s also a nuisance to have to have two different fuel mixes from weekend to weekend.) However, we generally ran more oil than Rotax calls for as extra insurance. That is, while Rotax officially calls for 50:1, we’d generally run more like 44:1, and even 35:1 for really hot days. I don’t know if that really helped, but it seemed like prudent insurance.
As for warranty coverage, Doug or one of the other Rotax service centers can give the authoritative answer on whether Motul is required in order for the warranty to be effective.
I have run RS-7 for the last 3-4 yrs with great success. I was at that GJMS race in 2005 and used the Motul but other than that particular weekend I have continued to use RS-7. Don’t be fooled, it is a good oil and when the bad batch came out we were notified. What more can you ask for?
Tom
@Tom Dennin wrote:
when the bad batch came out we were notified. What more can you ask for?
Tom
Exactly. Run either, they’re both good. Who supports us more? Or gives us swag?
I came across this site and link to some interesting information.
http://www.challengers101.com/EngineOils.htmlthe article is focused on ultralight/experimental aircraft engines. I use Pensoil in my experimental aircraft engine, a Rotax 503 DCDI, but I would not recommend that oil for karting. This is a larger, air cooled engine and max rpms are only about 6,500. Besides, it is a bit smokey. Just for reference though, I regularly run my cylinder head temps at 350 degrees, and reliability of my airplane engine is a Lot more important to me than a kart engine.
However, as the article states, a blend generally offers the best of both worlds. I know that Klotz offers a synthetic / castor blend and I am amazed that more people in karting don’t demand use of an 80/20 blend of synthetic / castor blend. The syn does a much better job of lubricating while the 20% castor both protects while the kart is sitting idle and it also has an extremely high flash point so it helps reduce damage during an overly lean run. The lower percentage of castor also reduces varnish.
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