Recently, we have seen the introduction of oil control systems in some vehicles, especially in General Motors and Mercedes vehicles (although I believe that BMW may have a similar system as well). Not all systems work the same. Mercedes actually has two slightly different systems, while General Motors’ system is the same for all vehicles (at least those that have it installed).

Mercedes calls its unit a “Flexible Service System.” The FSS in some Mercedes vehicles monitors actual oil quality as well as operating conditions (such as number of cold starts, average engine temperature, mileage driven, oil pan level, revolutions per minute, etc.). To measure the quality of the oil, there is actually a sensor that measures the electrical conductivity of the oil. The higher the conductivity of the oil, the greater the need for an oil change, according to Mercedes. Of course, this is probably not a perfect model and will not be as accurate as an actual oil analysis in determining true oil quality, but it is better than taking no measurements at all.

In any case, as the electrical conductivity increases, this value is combined with all the data from the operating conditions and is run through a special algorithm to determine if the oil is ready for a change. When a change is necessary, a light will flash on the instrument panel to indicate it.

The other Mercedes FSS unit, which will be somewhat less accurate, does not actually measure the electrical conductivity of the oil, so it is not testing the quality of the oil in any way. However, it measures all operating conditions and uses the algorithm to predict when an oil change will be necessary.

Actually, this is how GM’s oil control system works. It does not measure oil quality by electrical conductivity or by any other means. It simply measures operating conditions and “calculates” when an oil change should be necessary based on those conditions.

So how accurate are these units? Can they be trusted?

That is a difficult question to answer at this point. First of all, these systems have not been used long enough to have many solid statistics comparing vehicle / engine life with or without these systems in place. Second, many drivers do not trust the longer drain intervals recommended by these units and change the oil sooner anyway, offering, again, little data to show if the drain intervals recommended by these systems are conservative enough to keep engine protection equal to that obtained with shorter change intervals.

Since these units do not COMPLETELY measure oil quality, in the same way that an actual oil analysis would, they are unlikely to be completely accurate, but there is good reason to believe that they are quite accurate.

The problem, from my perspective, is, how were the boundaries set? Frankly, the best thing for vehicle manufacturers is if their engine performance begins to decline somewhere shortly after the 100,000-mile mark. Today, many people don’t expect a vehicle to perform much beyond 100K, so building a vehicle and recommending maintenance practices that will help the vehicle run longer is not in the best interest of OEMs.

So I’d be willing to bet that if you are someone who likes to maintain your vehicle as long as possible, the oil quality limits have been set at a lower standard than it would be appropriate to obtain. the maximum mileage of your vehicle. It really is only logical.

How many companies do you know today that incorporate MORE quality into their products than your typical customer expects? Not many. In fact, unfortunately, I’d be willing to bet that most of us could count on our fingers how many products we have purchased over the past year that offered BETTER quality / durability than we expected. Although this is a sad comment about the corporate world we live in today, it is a fairly accurate reflection of the attitude of most companies these days. Why would today’s automakers be any different?

Of course, with that said, I have no proof of the above statements. There do not appear to be any websites that collect oil analysis data from GM and Mercedes owners to compare REAL oil quality to “measured” by oil life monitors. Look. In fact, if you know of any, please let me know. I would love to see the results. I guess I know what they would be, but I’m certainly open to the possibility of being wrong.

I think the main thing to remember is that no one REALLY knows how accurate these oil monitoring systems are or how conservative their oil change interval recommendations are. Therefore, be careful how you trust your oil change interval recommendations.

Syn vs. Petro – Does the INITIAL quality of the oil affect the recommendations?

Well that’s an interesting question. Turns out these systems can’t tell if you have petroleum or synthetic oil in your crankcase, and this DOES make a difference. In fact, we can see this in light of a class action lawsuit that was filed against Mercedes Benz a few years ago.

Apparently the MB FSS assumes the use of synthetic oil in the engine. Most Europeans use synthetic oil by default, as typical oil change intervals in Europe are WAY longer than recommended here in the states (although that gap is closing). In contrast, most American drivers still use oil.

Well, there were no significant warnings to these MB owners regarding FSS units and the use of oil vs. Synthetic oils. Therefore, many users were using petroleum oils and using the FSS as a guide to know when to change their oil. Unfortunately, since the FSS was designed to recommend SYNTHETIC oil change intervals, these vehicles were producing severe sludge. Petroleum oil just couldn’t stand the oil change intervals recommended by the FSS. Bad news for your engine.

In the end, the vehicle owners won their lawsuit and a $ 32 million settlement was entered against Mercedes. My understanding is that MB is now very careful to make it explicitly clear what type of oils should be used in order to trust the results of its FSS monitor.

So it clearly makes a difference. And since these systems can’t tell what type of oil you’re using, you’ll need to adjust accordingly. As I understand it, GM units assume the use of petroleum oil (with the exception of vehicles that specifically require synthetic lubricants, such as the Corvette). So if you are using synthetic oil in a GM vehicle that does not specifically require it, the oil life monitor is likely to “go off” much earlier than necessary.

I heard that you can have the dealer adjust these units to account for the fact that you are using synthetic oil, but even then there are significant differences in quality from one synthetic to another so this may not yet be. completely accurate. . If you are using a premium synthetic oil that is designed for much longer oil change intervals (such as AMSOIL 25,000-mile oils or Mobil 1 Extended Performance 15,000-mile oils), the unit will most likely “trip” before necessary. However, you will at least know that you have a considerable margin of error due to the improved quality incorporated into those oils.

Conclusions on oil control systems and drain intervals

It is difficult to say for sure whether these oil monitoring systems are accurate or conservative enough to completely rely on recommended oil change intervals. It seems like the best advice we can give is that if you intend to drive your vehicle as long as possible and are looking for the best possible protection, you probably want to be more conservative than what your oil control system will be. You may want to wait for the monitoring system to “mark” the oil as ready for a change once or twice to get a better indicator of your change interval decisions.

If you are driving a Mercedes or GM vehicle that requires the use of synthetic, make sure you ARE using a fully synthetic oil (not just a blend, it is not the same), if you are going to do this.

If the manufacturer requires / recommends synthetics and you ARE using a “commercially available” synthetic oil, it would be a good idea to use the oil monitoring system’s change interval recommendation as a base (assuming your driving habits remain fairly constant) and then cut it back by at least 25% for later exchanges for the best protection. In other words, if you let the monitoring system run until it says “change oil”, and it shows a sign at 10,000 miles, then you should consider doing roughly 7,500 mile intervals to stay conservative.

If the vehicle manufacturer requires / recommends synthetic oils and you are NOT doing so, I recommend that you reconsider your position. First, if the manufacturer “requires” the use of synthetics, you are putting your engine at risk. OEMs DO NOT REQUIRE synthetics unless they have had problems with petroleum oils before. If you decide to go that route, understand that you are definitely putting your engine at risk.

If synthetic is simply “recommended” then it may be fine to use petroleum oil, if that is your decision, but it would be a good idea to have the dealer adjust your oil monitoring system to account for your petroleum oil usage. If they can’t or won’t, consider using a synthetic oil or don’t use the oil control system as a judge in determining when to change the oil.

If there is no specific recommendation or requirement to use synthetics, then the oil change interval specified by your oil monitoring system will be based on the assumption that petroleum oils are being used. If you ARE using petroleum oil, do as suggested above. Get a baseline and then cut back at least 25% for better protection. If you are using a synthetic, ask your dealer to adjust the unit to account for this. Then whatever range the unit suggests, again cut it to about 25% or more for better protection.

And, if you are using one of the AMSOIL 25,000 mile products, which are recommended / guaranteed for that interval, then you can choose to use that recommendation OR the oil change monitor recommendation. More often, in this case, the oil monitor recommendation will be a SHORTTER drain interval than AMSOIL’s recommended, so if you go that route, you’ll simply go wrong on the conservative side.