engine oil change on a 1985 Honda VF700C Magna.
Lucas Oil has been in the high-performance lubricants biz for a long time. Founded in 1989, the Indianapolis-based company has been on the cutting edge of product development and improvement, often through the experience gained from the torture-testing of heavy-duty trucking, agricultural machinery, and racing. That experience has translated into some top-line performance products for your street ride. We looked at a couple of those products—Lucas High Performance Synthetic Motorcycle Oil (10W-40) and Lucas SAE 75W-90 Synthetic Gear Oil—for use in my 1985 Honda VF700C Magna.
Despite being nearly 40 years old, the Magna is an excellent platform for considering these advanced products. It has a liquid-cooled DOHC V4 engine that cranks out a claimed 82 horsepower at 9500 rpm, has a 10,000 rpm redline, and is equipped with a shaft drive. According to product literature and the product label, Lucas Oil’s full-synthetic motor oil is formulated precisely for those engine properties.
The rear drive-gear unit contains the helical gear set that gets that horsepower to the rear wheel and must operate under tremendous stress where the drive gears mesh. That requires the use of oil with a high viscosity index and high lubricity to prevent excessive friction, heat build-up, and wear over the long haul.
Another factor in using full-synthetic lubricants in a bike such as my high-mileage Magna is the need for optimum friction protection. The motorcycle has nearly 50,000 miles on its all-original engine and drivetrain. After that many miles of service, the driveline components have worn enough to have the potential for part-to-part clearances slightly greater than original spec. That can lead to increased wear if the lubricants break down quickly because they can’t handle the heat and friction. Full-synthetic oils are less susceptible to deterioration and can offer longer service life between oil changes for the engine and drive gear.
This is where the how and why of synthetic vs conventional oil comes in. In terms of molecular structure, synthetic oils provide uniform, engineered structure; conventional oils are made up of non-uniform, random-structure molecules.
In lab tests commissioned by the American Automobile Association (AAA), using American Society for Testing and Materials (ASTM) methods, on average, full-synthetic oils outperform conventional oils by 47 percent on properties such as shear stability, deposit formation, volatility, cold-temperature pumpability, oxidation resistance, and oxidation-induced viscosity changes. Additionally, the additive packages used in full-synthetic and conventional oils will affect performance.
Some synthetic oils are made from base oils obtained from crude oil, categorized by the American Petroleum Institute (API) as Groups I through III. The most common base oils are Group IV, which do not contain a conventional oil base and are fully synthetic, known as polyalphaolefins (PAO). Group V base oils contain diesters and polyol.
The products we’re looking at are the Lucas SAE 75W-90 Synthetic Gear Oil, which is formulated using Group III, IV, and V base oils, plus Lucas High Performance Synthetic Motorcycle Oil, which has API Group III base oils.
Conventional oils are generally more susceptible to degradation due to oxidation and contamination when exposed to combustion byproducts. That can lead to the development of varnish, sludge, and other deposits in the engine, as well as reduced lubrication effectiveness.
The higher viscosity index (VI) typical of full synthetics means they are more stable, creating lubricant flow at high and low temperatures and better lubricant film thickness between sliding or rotating metal-part surfaces—a crucial wear-prevention factor. These two characteristics give full-synthetic lubricants longer service life expectancies between oil changes.
The viscosity index for the 10W-40 engine oil is 189 (typical conventional 10W-40 comes in at about 160), and the viscosity index for the 75W-90 gear oil is 145 (typical conventional gear oil comes in at about 150). The higher the VI, the greater the stability of the oil’s viscosity through the temperature range. A higher VI is necessary for engine oil because engine temperatures are much higher than the rear gear drive unit. Disadvantages of full-synthetic lubricants include generally higher cost than conventional oils for the same application, and the potential for additive separation at very low temperatures for extended periods.
Generally speaking, sticking with your machine’s manufacturer’s recommendations for the specifications of lubricants and service intervals for each application is the way to go. For a new bike, you have your warranty coverage to consider, though new motor oil specs probably require the use of at least semi-synthetic oil.
Full-synthetic oils were not in general use when my Honda VF700C Magna was manufactured, so the recommended lubricants and service intervals were all based on conventional oils. My bike is long out of warranty, so I want to protect that expensive-to-repair-or-replace engine and drivetrain; switching to full-synthetic products makes sense.
It’s important to note that Lucas Oil offers two variants of 10W40 full-synthetic motor oil. One variant has moly additives and is not recommended for use in engines with wet clutches. The other does not contain moly and is formulated for compatibility with wet clutches—as is the case with my VF700, so that’s what we’re using.
The engine oil and filter change process on the Honda V4 is common—there’s a spin-on oil filter and a 17mm hex sump drain plug on the bottom of the engine. However, there is a second 10mm hex drain plug on the front of the forward cylinder head. Removing that plug drains about half a cup of oil that would remain in the cylinder head without that second drain point. With a filter change, the engine takes 3.1 quarts of oil.
The rear drive-gear unit has a 6mm Allen head drain plug on the base of the housing and a 17mm hex filler cap. It takes 110cc of gear oil, which I find is easier to install with precision and without spilling using a 60cc syringe available from a pharmacy.
This is the first use of full-synthetic lubricants for my Honda’s V4 engine and rear final drive unit, and I’m very interested in two things—long-term value and short-term indications of performance changes. As mentioned, the engine oil service interval will be longer, but I’ll check the oil level and clarity often. Also, ExxonMobil suggests more frequent oil changes when transitioning from conventional to synthetic motor oil, as the synthetic oil will clean up deposits that will end up in the oil filter. The rear drive unit oil will also go to longer service intervals, and the clarity of the oil at the next change will be of interest.
One thing that I’ve noted in my first days of riding after using Lucas High Performance Synthetic Motorcycle Oil (10W-40) and Lucas SAE 75W-90 Synthetic Gear Oil changes has been the minimal heat to the touch of the rear gear unit at the end of the day. This is strictly subjective as I don’t have actual temperature readings of the rear unit post-ride with conventional hypoid gear oil to compare with. However, I do recall the rear unit being quite warm to the touch in the past with conventional oil; with the full-synthetic oil, it has been only lukewarm to cool. That may be expected, as minimizing friction and heat build-up are key claimed benefits of using full-synthetic. I’ll keep you posted.
