No, you don’t need racing oil in your daily driver

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Engineering Explained

If there is one tired-out thought that needs to go away in the car world, it is that race car parts always make a street car better. The vast majority of the time using speed parts on a street car creates a machine with a lot of compromises—which is not in itself better. Giant camshafts are the prime example. Huge overlap and lift numbers make for a brutal, head-turning idle—if the engine will idle at all—as you arrive at the Friday night cruise-in, but it will also make low-speed driving an exercise in frustration. Why someone would willingly submit to that is beyond me, but there is one popular trope where I have understood the hype on even though the hype is misplaced: Racing oil is no better for your street engine than regular oil.

Racing oil is designed for the extreme existence a race engine lives. Wide-open throttle, high temperatures, and tight tolerances are the norm. So is regular service. For instance, as Jason Fenske explains in a recent Engineering Explained video, NASCAR engines are only expected to last 1500 miles before a complete tear-down and rebuild. That means teams and engine builders will use the thinnest oil that will still keep the engine together for 1500 miles since there is less friction loss with that thinner oil. Less friction loss equals more power.

Interestingly though, as Fenske talked with Mobil 1 engineers he learned that racing oils contain many of the same additives as consumer-grade oils. The only exception was a pour-point depressant, which makes the oil thinner in cold temperatures. Most race engines never see cold temps. If they do, they’ll pre-heating the oil before engine startup which prevents wear.

Bringing up wear prevention introduces why most self-proclaimed “oil gurus” will tell you to use racing oil—zinc content. Also known as ZDDP, this additive helps prevent metal-on-metal wear by creating a sacrificial layer that builds up with heat and can be worn down and built up infinitely. This is most important for high-pressure metal contact points like flat-tappet camshafts and lifters. The general rule of thumb most folks will tell you is the more ZDDP, the better. It’s not that simple though.

ZDDP is short for Zinc dialkyldithiophosphates, and it’s the very end of that very intimidating to pronounce compound that creates the problem. The phosphates can ruin modern emissions controls equipment like catalytic converters, even in the minute amounts that stay on cylinder walls as the piston travels up and down in the cylinder. Since the vast majority of oil is sold for use in late-model vehicles, that is a problem. That ZDDP is also not as important since nearly all modern engine designs have left flat-tappet camshafts behind in favor of roller versions that reduce friction and increase service life.

That leaves us classic owners out in the cold a bit, right? Well, sort of. The key to remember here is that ZDDP is only important in situations of metal-on-metal contact, specifically when there is a lack of the proper oil film between parts. In a properly functioning engine, the ZDDP is a great safeguard, but not nearly as critical as internet experts might have you believe. Some is good, which is why most modern oils still contain ZDDP. Race oils tend to have about double the amount compared to oils for production engines.

Our vintage rides likely don’t have emissions equipment to worry about, so the drawbacks of extra ZDDP don’t really exist. Over-the-counter additives are the solution for those fretting about engine internals, but in the vast majority of cases keeping fresh, clean, high-quality oil in the crankcase will be sufficient to keep our beloved engines running for many years. These are street cars, and the use of racing parts or oils is often just a more expensive way to do the same thing.

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