Skip to content

DOWNTIME – Operating Temps and Automotive Oil

The process of pouring new oil into the motorcycle engine. Motorcycle service.

I have a 2000 Ducati Monster 750 which does not have a temperature gauge. How do I determine when it has warmed to operating temperature?

Can I use an infrared thermometer and, if so, do I take a reading at the header, crankcase, valve covers, etc.? —Mark Loftin

On air/oil cooled engines like your Monster, you can put your hands on the cooling fins until it is too hot to touch, which means it’s hot enough. While not exactly a scientific approach, it’s effective.

The goal of running the vehicle to operating temperature is to heat the engine enough to evaporate volatile contaminants, such as water and fuel. It also lubricates and protects metal parts from oxidation and conditions seals. Doing this regularly will keep components in great condition for years.

ASTM C1055, “Surface Conditions that Produce Contact Burn Injuries,” suggests 140 F is the average temperature a person can touch for five seconds without injury. Above this is what most technicians consider operating temperature on air or oil cooled engines.

If it’s too hot to touch the cylinder, it’s hot enough. Internal temperatures should be higher, enough to evaporate some or most of the volatile contaminants. It doesn’t need to boil.

Water and fuel evaporate at room temperature, and faster with heat. Oil pressurizes, lubricates and protects metals within seconds. A minute or two of pressurized oil should be enough time to nourish seals, assuming the oil additive package is still good. All this occurs within the warmup period.

Liquid-cooled vehicles are a bit different. Surface temperatures take longer to become hot to the touch, because of the coolant gap between the cylinder wall and outer shell. Also, the system prevents coolant flow until the temperature is hot enough to push open the thermostat valve.

For liquid-cooled vehicles, let the engine run for a couple of minutes then follow with a hand check on the radiator. Consider it warm as soon as the temperature begins to rise in the radiator.

On vehicles that have an internal temperature gauge, 180 should be reasonable for both liquid and oil cooled vehicles. Those with automatic chokes, will indicate warm when the vehicle drops off fast idle. Vehicles with electric fans will usually kick on about 200-230 F. At this point it is considered hot, but could be used to verify it’s fully warmed up.

Also, consider installing an oil cooler fan kit if you don’t already have one, particularly if you sit in stop-and-go traffic for long periods. Even liquid and fan cooled system can heat soak and overheat the exhaust valves and immediate areas if idling and unmoving for extended periods. This is especially true on closed-course engines (off-road) that can produce glowing red pipes within a couple of minutes.

A fan and oil or liquid cooling system keeps the cylinder and head cool, but external plastics, rubbers, electronics, internal oil and the bottom-end can increase beyond coolant temperatures from combustion and exhaust heat conduction.

If you plan on idling for a while, run the bike stationary until warm, then use a blower fan (above) toward the front of the vehicle or ride the vehicle at 20 mph or faster to keep unmanaged areas cool. Technicians typically use a floor blower when extended idling periods are required (e.g., intake synchronization), regardless of cooling system type.

I’ve had issues with the accuracy of laser pointer temperature guns. I use them as a diagnostic tool to look for substantial differences between exhaust temperatures to indicate running issues.

Point the gun 90 degrees to a flat point on the side of the cylinder. Measure toward the center of the cylinder and at least a few inches away from any exhaust manifolds. Try to keep radiant heat away from the pointer trajectory. For instance, avoid measuring above a hot exhaust manifold.

Avoid irregular angles and reflective surfaces such as chrome or glossy paint. Aim for an external temperature above 140 F. —Kevin O’Shaughnessy

Rotella T4 is rated JASO MA/MA2. I have been using Rotella for years in all kinds of bikes. My BMW service tech insists on using BMW oil. His argument against Rotella is that the bike has a wet clutch.

The other bikes I have used Rotella in have had wet clutches, and I haven’t had a problem. Is he correct, or is there something special about BMW wet clutches? —Bill Heil

Oil is not magic, it’s chemistry for specific purposes. Vehicles such as the SV650 and VFR750 contain wet clutches, integrated transmissions and flat tappet cams. These are common Japanese motorcycle engines, with dynamic conditions that require specific protection.

Many motorcyclists believe any Rotella, Mobil 1 or diesel oil is suitable for this type of engine, but most blends are not. As shown in the chart (right), only Rotella T4 15W-40 and T6 5W-40 are JASO MA compliant. Only Mobil 1 4T is JASO MA compliant.

The Japanese Automotive Standards Organization (JASO) MA, includes testing to support wet clutch engagement (friction/grip requirements), flat tappet cams (wiping load) and integrated transmissions (gear load).

Most automotive engine oils do not have the protective elements needed for flat tappet mechanisms. Synthetic oils are not necessarily the fix. The focus should be on what happens over time.

We can put straight 30 grade automotive oil into a GSXR, and it will it work. It even has an adequate film barrier, antiacid, emulgents, anti-foam, detergents, seal protectants, and anti-oxidizers. What it doesn’t have is the right chemistry of sacrificial additives.

These additives insert and sacrifice themselves between crushing parts, to vanquish adhesion-galling and self-destruction. Without these additives, the engine will work, but won’t be protected as well or for as long. More wear will take place and the engine life will be shorter.

Automotive engines reduce friction with high-mass roller elements between wear points, often via roller rocker arms and/or roller lifters. These work efficiently at low rpm and require less “wipe” protection.

Many wet-clutch Japanese bikes and some BMWs run at higher rpm and require lower mass (nonroller) wiping mechanisms. Air cooled V-twins often use dry or semi-dry clutches, but still have integrated transmissions or flat tappet wear points.

The additive used to protect these systems is primarily zinc-dialkyl dithiophosphate (ZDDP), which has a triple duty of being the sacrificial additive, minimizing lubricant breakdown and as a friction modifier for wet clutches. There are fast-acting, higher performing (expensive) and slow acting, lower-performing (inexpensive) ZDDP. All types will show up the same on oil tests, but they don’t perform equally.

Testing standards such as JASO MA could be passed and have mixed results in application. When testing Rotella, I found some cam-against-bucket engines that dropped ZDDP with an increase in metal wear before the service interval.

Other cam-against-bucket and rocker arm configurations, were able to use Rotella for the entire duration with ideal wear. I was unable to determine why, but it could be the gears, cams, or other factors.

In all tests, Rotella ZDDP levels dropped faster than motorcycle-specific brands, though only an issue when wear metals increased.

There is nothing special about a BMW wet clutch. JASO MA is equivalent to ISO-L-EMA, as is MA1 and MA2, which use the same SAE No. 2 friction test and parameters. The oils are interchangeable.

Try any oil rated for your engine, Rotella, Yamalube, BMW, AMSOIL, etc. Take oil samples and see how long each last and perform. You may find long term savings in a higher cost oil.

I didn’t have clutch engagement or clutch wear issues with MA rated Rotella, though with any oil change, the engagement characteristics may
feel different. —Kevin O’Shaughnessy

Kevin O’Shaughnessy is curriculum developer at Motorcycle Mechanics Institute, formerly R&D at Race Tech.

You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *