Dry Sump Vs. Wet Sump Oil System: What’s The Difference?

Your engine doesn’t enjoy oil starvation. Sure, you could run dangerously low on oil and get away with it, but don’t count on it. Let the oil flow, friends, whether your vehicle has a normal wet sump oil pan or a more advanced dry sump system. 

A standard wet oil sump is fine for most normal driving conditions where G-forces are limited to those that pull everything toward the center of the Earth. In a wet-sump system, there’s an oil pan under the crankcase where all the engine oil sits. An oil pump sucks the oil out of the pan and routes it through various oil passages to locations such as the cylinder walls and connecting rods. It’s a fine system.

However, let’s say you want to accelerate, decelerate, or corner with force. Well, the oil in your wet-sump system could move so far from the inlet to the pump that it literally can’t deliver that life-sustaining, cooling, and lubricating oil anymore. A dry-sump system solves this problem by taking all of that oil and placing it in a remote tank so the pump always has a steady supply. There’s no more big old oil pan with oil sloshing around, and you can now spend the day on a skidpad without fear of starving your engine.

Okay, so we’ve covered how dry sump systems keep the essential spinning parts well lubricated and cool during extreme G-loads, but there’s so much more. For instance, check out that diagram and notice how the crank doesn’t have to continually spin in a bath of oil, which reduces drag. Also, by moving the engine’s oil to a remote tank, engineers can better tailor a car’s weight distribution and lower the center of gravity for superior handling and acceleration. Have a front-engined nose-biased car? Move all that oil toward the rear. While you’re at it, you could give it a transaxle and move the battery to the back, too.

Dry sump systems also let you give a car way more oil than it could otherwise have. Take the awesome Mercedes 450SEL 6.9. Not the still cool, pleasant-but-slow, luxurious for the time normal 450SEL, but the monster 6.9 that memorably tore up roads in John Frankenheimer’s “Ronin.” These 6.9s had dry sump systems with a gargantuan 12.7-quart oil tank. With that much oil, the system can more effectively manage oil temps and keep the oil good for longer. 

Say what you want about 450SEL 6.9s and their ludicrous maintenance needs, but they can go 12,500 miles before they need an oil change. Beyond that, these things were made in an era where 3,000 miles was still the norm.

Dry sump systems sound awesome, so why aren’t dry sump oil systems in everything? Well, they’re expensive to produce since they require more parts, such as a dedicated pump, extensive piping, and, of course, a reservoir. Those parts also introduce more failure and maintenance points. Packaging also becomes a concern because the designers have to figure out where all that stuff has to go. 

If a car is just going to live out its life ferrying kids to soccer or hauling groceries, there’s no need for an exotic piece of racing kit to complicate things and drive the price up. Plus, manufacturers can still make wet sump systems work well enough. Look at Ford’s FE 427. The early top-oiler models couldn’t keep the crank bearings lubricated during circle track driving, so Ford developed the side-oiler to keep the crank properly lubed. Problem solved, the engine did just great after that.

Who am I kidding, though? For enthusiasts, well enough doesn’t cut it. Corvettes got them in the C6 generation for the ZR1, Z06, and manual-equipped Grand Sports, a trend that continues in the current mid-engine C8 Corvette’s LT2. The Maserati Ghibli — the good one from the ’60s and ’70s – got dry sump lubrication to keep the engine low in that sexy, sexy swooping front end. Alfa Romeo’s Matta, which was basically an Italian Jeep, featured a dry sump system in the 1950s to keep oil flowing no matter the angle. 

So go ahead, install that dry sump system in your Miata and prep it for sustained 1G turns. It’d be so sweet.