The International CBX Owners Association

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Motorcycle vs. Automotive Oils

What Motorcycle Consumer News Didn't Tell You

Tim Ware, Former ICOA National Director

I've always been a believer in motorcycle specific oils and believed the claims made by the manufacturers. Maybe I just wanted to believe their claims and that was enough for me. I've used Golden Spectro 20-50 synthetic petroleum blend for ten years and just couldn't find any fault with it. Then along came the Motorcycle Consumer News article in February of 1994 and it appeared to disclaim everything I believed in. Although I read it, for some reason I just wasn't convinced (or maybe, once again, I didn't want to be convinced). During the next three years, I heard people talking about changing to Mobil 1 synthetic. But they never made any great claims, just that they switched. Was it better, or just cheaper at Wal-Mart? Well, this year I was determined to find out if Mobil 1 was actually as good or better than Golden Spectro in my own unofficial and crude seat-of-the-pants experiment.

I always change my oil in the spring right after a 5-10 mile warm-up ride, so this seemed the perfect time to try the Mobil 1. New Mobil 1, new filter, and out I went. No surprises, no changes in oil pressure or temperature (I use VDO gauges for both) and everything seemed OK. I drove the bike normally and noticed that shifting was a little more notchy, especially at low rpm's.

No big deal. This could just be attributed to my steady loss of memory as middle-age has its affect on me. I left the oil in for about one week before running the bike through four gears at 9,500 rpm's. What was wrong? It shifted OK at that rpm, but something was missing.It felt more like an automatic transmission than the "Bang" I would normally feel when hitting the next gear that hard. Tried another run, and the same thing. Then I remembered Kevin Sheard telling me that he tried Mobil 1 in his nitrous CBX and that the clutch would just spin whenever he hit the nitrous button. What's going on here? I went home, dumped the oil, filter and oil cooler and refilled the CBX with Golden Spectro 20-50. No more notchy shifting and a good snap when I released the clutch! Could there be something about this automotive synthetic when used in motorcycle transmissions/clutches that Motorcycle Consumer News didn't tell us?

About this same time, three different independent articles appeared in national magazines about the dangers of the new automotive oils. So I decided to read the Motorcycle Consumer News article again to see if I missed something. The entire article seems to be obsessed with viscosity retention" and gives very little importance to anything else. I also was confused about why MCN chose Mobil 1 synthetic against Spectro's regular petroleum oil. This didn't seem fair. MCN tested five oils: Mobil 1, Castrol Syntec (synthetic), Castrol GTX (petroleum), Spectro 4 (petroleum) and Honda HP4 (synthetic). The Mobil 1 and Castrol Syntec scored highest in viscosity retention. I felt that more digging was necessary. Some quotes from the MCN article:

"Claim - Since the introduction of catalytic converters in automobiles, the best anti-wear agents have been limited by law to the amount that can be used in automotive oils, but are present in greater concentration in motorcycle oils."

"Fact - Phosphorous deteriorates the catalyst in converters and is therefore restricted to a very small percentage in automotive oils. Phosphorous is also an essential element in one of the best anti-wear agents, ZDDP (zinc dialkyldithiophosphate), which is a primary component in such over-the-counter engine additives as STP Engine Treatment."

"While it is true that slightly increased concentrations of ZDDP are found in some motorcycle oils (such as Spectro Products), it is also true that these concentrations still fall under the government limits."

[Now, motorcycle oils have more anti-wear agents than automotive oils because they clog the catalytic converter. Hang on to this thought, because we'll use it later - Tim]

"Claim - Motorcycle engines run hotter and rev higher than automobile engines....

"Fact - This is one of those statements that was much more true in the 1970's than in the 1990's. The big, slow-revving Detroit automobile engines of the past have mostly been replaced with smaller, higher-revving four-cylinder and six-cylinder engines that have much more in common with their counterparts running on two wheels."

[This is where I take great exception to MCN's ignorant assumptions. Show me one standard production automobile that produces 150 horsepower per liter and revs to 14,000 rpm. Does MCN think that motorcycles stopped developing while automobiles continued? They make this foolish statement while printing the following contradictory claim - Tim]

Referencing an oil viscosity retention chart, the MCN states "Comparing these figures to viscosity retention for the same oils when used in an automobile.. would indicate that motorcycles are indeed harder on oils than cars."

They go on "...the Castrol GTX sample at 800 miles showed a relative viscosity of 0.722, meaning it had retained 72.2 percent of its original the motorcycle."

"Just for comparison sake, I also tested the viscosity drop of the Castrol GTX automotive oil after use in a 1987 Honda Accord automobile. At 3,600 miles of use, the Castrol GTX showed a relative viscosity of 91.8 percent."

[The bike runs 800 miles and retains 72.2%, while the car runs the same exact oil for 3,600 miles and retains 91.8% of its viscosity. Does this sound like a bike is harder on its oil and has special needs? This article was quickly becoming a testimonial to motorcycle specific oils rather than what it appeared to be the first time I read it. Viscosity retention seems to be the only interest of MCN and yet they compared an automotive synthetic against the leading motorcycle brand's petroleum! At this point, I believed that there had to be more to this oil story than MCN was telling us, But I didn't want to rely on the motorcycle oil companies since I also believed that they would say only what would benefit them. So I went back to the three independent articles for the unbiased data that was needed. - Tim]

The first article on this subject was from Bill Heald, contributing editor of Rider Magazine. Bill states:

"The oil you buy for your car is designed for automobile engines, and its additive packages reflect this. These days, the new American Petroleum Institute's "SJ" classified oils are especially formulated to help reduce internal friction in order to reach new corporate fuel economy standards. The additive packages in these oils are fine for your new Cadillac or Subaru, but in the quest to increase fuel economy and decrease emissions, they are getting away from chemistry that suits the high-temperature, high rpm conditions in motorcycle engines, particularly air-cooled ones.... The increased use of friction modifiers in this newest classification of automotive oils may also pose compatibility problems with wet clutches as well."

Heald concludes by saying:

"As to the question of whether you really need motorcycle oil, it's clear that the contents of the additive packages for car and motorcycle oils is predicated by different concerns. In the case of automobiles the latest lubricants are primarily designed to reduce internal friction and save fuel; whereas motorcycle oils are geared more toward handling high rpm loads while also operating in transmissions and wet clutches."

[This was starting to clarify some questions, but this was only one person's opinion. - Tim]

The following excerpt is from an article in Motorcycle Cruiser magazine titled The Trouble with Automotive Oil:

"Traditionally, a new API standard meant that the oil offered greater protection for the engine or other clear-cut benefits, such as longer oil life. However, recent API standards, specifically SH and SJ take a different direction. The problem stems from the automakers' need to reduce the fuel consumption of their vehicles and to protect their catalytic converters. Government corporate fuel economy (C.A.F.E.) standards drive the requirement for oils that improve mileage. To reduce fuel consumption, automakers have moved toward oils with friction modifiers to reduce viscosity and friction. These so-called 'energy-conserving' oils have three levels of friction reduction."

"To protect the catalytic converters (which by law must be guaranteed for 100,000 miles) automakers specify oils with little or no zinc or phosphorous, the most effective extreme-pressure (EP) and anti-wear additives."

"With the API, SH and the new SJ standard, automotive oils have begun to cause problems in motorcycle engines. Oils with friction modifiers cause slippage of clutches, starter clutches and back-torque limiters. In addition, transmission gear and camshaft wear, as well as pitting, have increased with the absence of antiwear and extreme-pressure additives."

Motorcycle Cruiser concludes with: "Even some of the big oil companies, such as Castrol and Pennzoil acknowledge the situation by making motorcycle-specific oils. It's no longer wise to use current standard automotive oil in your motorcycle. The money you save on the oil purchase is lost in damage to your engine and drive-train."

Gordon Jennings of Motorcyclist magazine recently wrote on the subject in his article Energy Weenies Strike Again:

"...motor oils are supposed to do four important things: cool, seal, cushion and lubricate. The government now has effectively decreed that low fluid drag shall be more important than any of the other oil properties. I am concerned that reduced engine life will prove to be a side effect of compounding oils for low drag."

"Automobile manufacturers.. have wrung about all the mileage increases they can get from improved combustion and mechanical friction reduction. So they now venture into what may be over-reliance on chemicals to satisfy miles-per-gallon targets of weenies who give no thought to miles per engine."

"I believe we have arrived at the point where motorcycles' motor oil requirements are not all met by the new oils made for cars. Some divergence appeared when the Feds limited levels of phosphorous compounds like zinc dialkyldithiophosphate in motor oils to avoid poisoning catalytic converters, which most motorcycles don't have."

"Most motorcycle clutches run in oil, which means the friction modifiers in the latest energy conserving motor oils could cause clutch slip. People have been worrying about lubrication-caused clutch slip for years, and I have been telling them it's a non-problem for just as long. Today I'm not so sure. Motorcycle manufacturers have begun to worry about the direction the latest general-use oils are taking, foreseeing clutch and other problems."

"...the motor oils of the recent past were superb. Those are the oils your motorcycle's manufacturer has recommended, and you can't get into trouble using them. But those oils are on their way to being things of the past, like leaded fuel, doomed by bureaucratic tunnel vision."


  • The development of new oils using friction modifiers that improve mileage in automobiles has created a problem for motorcycles. Perhaps automotive oils of a few years ago were acceptable, but the new SJ and SH in particular have motorcycle manufacturers worried. So worried, in fact, that representatives from Honda, Kawasaki, Yamaha and Suzuki participated in a SAE (Society of Automotive Engineers) study in May 1996 to evaluate the problem of friction modifiers and their effect on motorcycle engine performance and life.

  • It is now a fact that friction modifiers used to improve automobile mileage will cause slipping clutches. This is a problem for CBX owners because our engine clutches run in oil and our alternator is driven by a steel clutch that also is in a constant oil bath. A slipping engine clutch may be an annoyance, but a slipping alternator clutch means a reduction in charging, unusual noises and excessive wear.

  • There is no doubt that the synthetic or synthetic blends are far superior to a pure petroleum oil, Just make sure it's designed for a motorcycle.

  • The absence of zinc and phosphorous from automobile oils is for the preservation of catalytic converters. These are both extreme pressure additives that are a necessary part of motorcycle oils.

The final decision is yours. You may not have a problem now and feel quite content using automotive oils. But three independent magazines and the motorcycle manufacturers are all warning us that we could experience expensive problems down the road.


I don't want to take that chance.

Click here for a lot more information on the nature of Motor Oil.

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We've lately received the following correspondence about Tim's article, and we'd like to share it with you.

June 18, 1998
To the CBX Club,

After reading your story on oil I thought I would offer up my experience in the area. In '77 myself and 3 buddies all purchased new RD400's. after a short while one of then got a set of pipes, making his quicker and faster than the rest. Be a reading buff I remembered a comparison of Mobil 1 to convention oil in Popular Science. After 100,000 miles the Mobil 1 auto engine after tear-down (oil was changed every 25k) clean, shiny, and the parts were within new car spec's. It also ran cooler due the friction loss. So I tried it in my RD. it worked great at first (+800 rpm in 6th) and now my bike was quickest. But shortly my clutch started slipping. I replaced with a kit from Barnett, new plates and springs. I never had a clutch problem again. The bike was later heavily modified with professional help, it would and did outrun any 750 from that time period and never again required clutch work (but it was stolen in '81).

In '78 after reading the Cycle story I got on a waiting list and eventually received one of the first "Glory Red" CBX's in SoCal. After a length break-in (I always held the belief that the rings may not properly seat when using a synthetic so I always use conventional oils for the first 3-5K miles. I have no proof of this but I follow it to this day.) As a precaution I upgraded the clutch prior to using Mobil 1. Being a crazy high performance loving 19 year old I hooked up with Dale Walkers HP performance and started fixing it up. ( 6 into 6 Denco's (loved them!) air-box mod's, Nitrous, suspension mod's (I like corners!), paint by Santini (he does funny cars now) etc..) [John's CBX can be found in Your CBX - Webmaster] I put a good 20K miles on in a year and a half. Never had any oil related problems. Unfortunately I was a 19 year old with out a good job so I lost it to the Bank!!! It was the worst time in my life.

Anyway I'm close to 40 now. I've had many bikes since that CBX but none compare. I hope to pick up a clean red '79 in the next year or so at which point I will join your club. I found the oil story very informative and will use for reference. Keep up the good work.

John Tami
Mission Viejo, Ca.

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Reprint courtesy CBXPress (c) International CBX Owners Association 1998

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