C6-C8 Corvette Dry Sump Oiling System Service

by Hib Halverson

Engines with dry-sump oiling systems have been either optional or standard on Corvettes since 2006.

When a dry-sump engine is running, only a small amount of oil is in its oil pan, or “sump”, with a majority of the oil supply in a tank separate from the engine. One or more “scavenge” pumps suck oil from the sump and pump it to the oil tank. A “pressure pump” draws oil from the tank and pumps it through the filter and oil cooler to engine parts which are pressure lubricated.

Key advantages of dry-sump oiling are: 1) more consistent oil pressure when the engine is at high rpm and the car is maneuvering with high lateral acceleration and 2) far less oil aeration or “windage” caused by the spinning crankshaft and violent air movement between the cylinder block’s “bays” rapidly reciprocating piston movement.

Introduced on C6

GM’s first production engine with a dry-sump system was introduced back in the C6 era on the 2006 ZO6’s LS7 “Gen4” Small-Block V8. The system used one scavenge pump and one pressure pump. The oil tank was on the left side of the firewall, behind the right front wheel well. Two hoses connected it to the engine.

The C6 dry-sump system introduced on the 2006 ZO6. The C6 dry-sump oil pan. The C7 version is similar.

After introducing the dry-sump system for ’06, GM used it on the 2009 ZR1’s LS9. According to the Corvette Black Book (PN B-400), the oil tank capacity was also increased to support the piston oilers used to cool the supercharged engine’s pistons. All dry-sump engines, from ’09-’19, have that bigger tank.

The revised dry-sump tank was released in 2009 for the C6 ZR1’s LS9.

Starting in 2010, GM offered RPO Z52 on Grand Sport Coupes with manual transmissions. Z52 was a performance package that added dry-sump oiling to the GS’s LS3, as well as a rear axle cooler and a rear-mounted battery.

Expanded for C7

With the C7’s introduction in 2014, GM continued to expand the use of dry-sump oiling systems. Any ’14-’19 Stingray’s LT1 had a dry-sump if the car was equipped with the Z51 Performance Package. The LT4s in ’15-’19 ZO6’s and the ’19 ZR1’s LT5 were dry-sump engines. The C7 system was similar to that used on C6. The main difference was the oil pan which was altered to accommodate: 1) the Gen5 Small-Block’s oil-to-coolant heat exchanger and, 2) a revised pressure pump.

Standard on C8

The dry-sump system was completely redesigned for the C8.

All C8s are “dry-sumped”. For the mid-engine car, the system was completely redesigned. There are now three scavenge pumps.

The LT2 oil pan has two scavenge pump intakes and is shallower than the C6/C7 pan. That allowed the engine to be lower in the chassis which lowered the car’s center-of-gravity.

A third scavenge pump sucks oil out of the “valley” between cylinder banks that collects oil from the valve train. The oil tank is new and mounts to the front of the engine eliminating the hoses. Finally, additional scavenge pumps and no hoses allowed a reduction of oil capacity from 10.5-qts. to 7.5-qts. which makes the dry-sump tank smaller and lighter.

Oil Checking

Dry sump engines require a special oil level checking procedure because when the engine is not running, oil in the supply tank drains back into the oil pan. When that happens, the indicated oil level will be inaccurate. How quickly drain back occurs depends on whether the engine is in a C6/C7 or a C8. Rather than somewhere on the engine block, the dipstick for a dry-sump engine is in the oil tank, adjacent to the oil fill cap.

Before oil level checking, oil temperature needs to be about 175°F. The best bet is to drive the car until the oil temperature reaches that range. The oil may reach that temperature with the engine just idling, but it takes longer.

If you’re checking oil on a C6/C7 park on level ground, shut the engine off, wait five minutes, then pull the dipstick out of the tank, wipe it dry with a clean rag and re-insert it. Pull the stick a second time and observe the oil level in relation to the crosshatched part of the stick. The very bottom of the crosshatching is the one-quart low mark. Add a quart of oil when the oil level is at or below that. The add-one-quart mark is at the lower end of the crosshatched section of the oil tank dipstick of any Corvette engine with a dry-sump system.

With 2020 and up Corvettes, the oil check procedure is even more unusual because it’s done with the engine running at idle. The oil temperature needs to be about 175°F. Park on level ground. Leave the engine running. Pull the dipstick, wipe it with a clean rag, re-insert the stick, then pull it a second time. The very bottom of the crosshatched section is the one-quart low mark. Add a quart of oil when the oil level is at or below that.

The dipstick and the oil filler are at the right front of the engine on a C8. If the car has the “Engine Appearance” package the stick and filler are accessed through a hole in the right-side panel.

Oil and Filter Changes

Oil changes on Corvette dry-sump engines are also a bit different.

Depending on how low the car is and what kind of front spoiler or front splitter the car has, you may need to drive it up on ramps or bevel-cut sections of 4×4 to get the car high enough to roll the jack under it. Three inches is the ideal height for ramps like this.
On C6 and C7, the best way to lift the front is to put a length of 2×4 on the jack pad, then lift the rearmost of the two front cross-members. Put Zip Products Billet Aluminum Jack Pads in each of the front frame slots. Line up your jack stands with the pucks and lower the car onto the jack stands.
C6 and C7 oil pans have two drain plugs.
Do the front drain first. Use a 15-mm box wrench or socket to break the plug loose. Once the drain plug is dripping, you can keep your hands dry of oil with a tool like Matco’s “Drain Plug Pro”. It attaches magnetically and the flex-cable allows the user to remove the drain plug while keeping hands out of the oil stream.

If you have a really large drain pan, you can remove both and drain all the oil at once, but in most cases do them individually and start with the front plug which drains the tank. We use a 15-mm box wrench to break the plug loose, then we use a handy tool from Matco, the “Drain Plug Pro” (PN MST5911A), to remove the loosened plug without getting oil all over your fingers.

The front plug drains the tank and with 8 or so quarts of oil, there’s a lot of head pressure. Be prepared for it to shoot out, then have to move the drain pan as flow subsides. We take samples to send to Speediagnostix, an oil analysis laboratory. The easiest time to do that is at an oil change.

Spectrographic oil analysis is a great way to stay on top of the condition of your engine. In most cases, we send a sample to Speediagnostix at every oil change.

Once the oil flow reduces to an occasional drip, replace the drain plug and you might want to use a 1992-2019 Magnetic Oil Pan Drain Plug. It’s best to use a torque wrench. Tighten drain plugs to 18-ft/lbs. The rear drain plug allows whatever oil is left in the oil pan to drain. Reposition your drain pan and remove that drain plug in the same manner as the first one. Let it drain until there’s only an occasional drip then replace and tighten the drain plug. On ’09-’19s, if you find a torque wrench and socket will not fit between the drain plug and the oil cooler, use a 15-mm box wrench and your “muscle memory” to tighten it.

Move your drain pan under the oil filter. You’ll need an oil filter wrench designed for the smaller diameter filter used on C6 and C7 engines. A wide variety of these are available from automotive tool vendors. We like the “3-Jaw Oil Filter Wrench” from Matco tools (PN MST60C). It works well with the smaller diameter oil filters on contemporary GM engines. It fits a 3/8th-drive extension and it grips the filter tightly.

This is Matco’s 3-Jaw Oil Filter Wrench which can loosen just about any filter on a Gen4 or Gen5 Small-Block. Fit this tool on a 3/8-drive short extension. Stick that on a long-handled 3/8-drive ratchet and you’ll be surprised at how easy that filter comes off.

Use the Matco wrench to break the filter loose, unscrew it partway. Oil will begin to stream down the sides of the filter and into your drain pan.

Take a break while the engine’s oiling system drains through the filter.
Once the oil coming from the filter becomes a slow drip. Wipe the sides of the filter, put on some latex gloves, remove it, and pour the oil in the filter into your drain pan. Wipe residual oil off the filter sealing surface.

The car in these images is a C7, all of which, along with the ’20-’22 C8 Stingrays, have Gen5 (LT1, LT2, LT4, LT5) Small-Blocks. Their computer-controlled, dual-pressure oil pumps are sensitive to the pressure differential at which the filter’s bypass valve opens so the proper oil filter choice is important. According to a GM Service Bulletin, issued in July 2018, Gen5 oil filters must have a 22-psi bypass.

Good oil filters for Gen5’s are available from Zip Products. The first is the 2014-2021 PF64 Delco Oil Filter, the filter GM puts on Gen5’s at the factory. The other is the 2014-2021 WIX Racing XP Oil Filter, part of the Wix “XP” series intended for use with synthetic oil in street high-performance or racing duty cycles. Both those oil filters have the correct, 22-psi bypass valve.

ACDelco also lists its UPF64R “Gold Professional” oil filter for Gen5s in C7s, but its bypass valve opening is 60% higher, at 35-psi. Considering that July 2018, GM Service Bulletin, which cautions service technicians about filters not having 22-psi bypass valves, ACD’s listing of the UPF64R for Gen5 V8s in spite of its much higher bypass valve opening pressure has caused confusion in the Corvette community. As a result, the only two filters we recommend for use on a Gen5 Small-Block in a C7 or a C8 are the OE ACDelco PF64 or the high-performance Wix 10290XP.

Oil filters Zip Products offers are (L-to-R) The ACDelco UPF48R for the Gen4 V8 in C6’s along with the ACDelco PF64 and the Wix WL10290XP for C7’s and C8’s with the Gen5.

If you are changing the oil on a C6 dry-sump, Zip has those filters, too. We suggest either the 2006-2013 PF48E Oil Filter, the stock filter for Gen4’s in ’06-’13 Corvettes or the 2006-2013 UPF-48R Gold Series Oil Filter, which is ACD’s premium oil filter for street hi-po and racing use. Gen4 Small-Blocks are not as sensitive to the bypass opening. While the two ACD filters have somewhat different bypass specs, 23- and 15-psi. respectively, both are good choices for that application.

Prefill the new oil filter, in this case, a Wix 10290XP, with 0W40 engine oil. You must lubricate the oil filter’s gasket. You can use either engine oil, lithium grease or bearing grease.
Screw the new filter in place. Once the gasket touches the sealing surface, tighten the filter 3/4 to one turn. We filled this engine’s dry-sump system with Driven DI40 0w-40 Synthetic Direct Injection Performance Motor Oil and intended for use in direct-injected V8s. We prefer DI40 for its better shear stability which reduces viscosity loss during each drain interval.

The ’06-’08 ZO6 dry-sump system’s capacity is 8-quarts including the filter change. The dry-sumps on ’09-’19 dry-sumps have a capacity of 9.8-quarts, including the filter. From either of those numbers, subtract the amount of oil used to pre-fill the filter, then add what’s left–should be approximately either 7.5 or 9.3-qt– to the engine through the oil filler in the top of the dry-sump tank. Some dry-sump engines have a removable cap on the passenger side rocker cover. Do not use that as an oil filler. You may damage your engine if you do so. In the C6 ZO6 era there was a rash of problems with folks, from DIYs to professional service techs, doing that by mistake. Don’t be one of those people.

Warm the oil to 175°F either with a road test or a long idle time. Shut the engine off. Wait five minutes, then check the oil. It should be at or near the top of the crosshatched portion of the dipstick. If that’s where the level is, you’re done.

The 2020-2022 C8 Corvette has a different dry-sump system, so, expectedly, the oil drain procedure is different. Not only that, because the C8’s underbody structure varies so much from that of C6/C7, the jacking procedure is quite unlike that required by its front-engine predecessors. We’ll tell you right up front that oil and filter changes for the engines in C8s are far easier on a drive-on hoist or a twin post lift that comes in from the side.

Nevertheless, a lot of we DIY’s don’t have hoists. Fortunately, it is possible to lift the back of a C8 with a floor jack and support it with jack stands, but the process a bit more work than it is with C6 or C7.

If you lack a hoist or a lift, to get the rear of a C8 up on jack stands, you first have to drive the rear wheels onto low ramps. After the rear wheels are on the ramps, you must chock the front wheels.
To gain access to the C8’s rear jacking points, you must remove the rear underbody air deflector panel. It uses two types of fasteners. Eleven hex head bolts and a single plastic retainer.

To lift the back of a C8 without a hoist, use the jacking points specified by GM Service Information (GMSI) which, in the rear, are the ends of the C8’s rear crossmember. GMSI is the same service data GM dealer service techs use. Subscriptions are available to consumers. The cost is as low as $20 for a three-day subscription. See AC-Delco’s Technical Delivery System (TDS) web page for more information. Install two, jacking pads in the rear frame slots. We set an aluminum “spacer” on our jack pad. A small block of hardwood or a hockey puck would also work.

We rolled the floor jack under the back of the car and carefully positioned the jack pad so the puck would lift the corners of the C8’s rear cross member. Do not position the jack to lift on the rear cradle shear plate.

Start with the right side. Lift the right corner of the cross member enough to get a jack stand set on its lowest height under the jacking puck on the right side and release the jack to set the puck on the stand.

Using two jack-stands, lift and support the car in two stages as discussed in the text.

Move the floor jack to the left end of the rear cross member. Jack that side up such that you can get a jack stand, set two notches higher than the first one, under its jacking puck.  Set the left side of the car down on that stand. Finally, go back to the right side, jack the right side up higher, raise the jack stand two notches. Release the floor jack and roll it out of the way.

The C8’s oil drain and oil filter are accessed through ports in the rear cradle shear plate and the underbody rear air deflector. Take care during the oil and filter change to not make a mess because to clean it up, you’ll have to remove both the shear plate (shown) as well as the underbody rear air deflector.
Use a 3/8-drive, 15-mm socket to break the drain plug loose. Draining the oil is almost impossible without getting it all over one’s hands and making a mess on the top of the shear plate unless you use a tool like the Matco “Drain Plug Pro” for drain plug removal. C8s have only one oil drain.
A C8 drain plug has a rubber o-ring at the top. Sometimes that o-ring makes reinstalling the plug a bit difficult. Push hard and the o-ring will pop into place. Tighten to 18-ft/lbs.
Matco’s Oil Filter Wrench is a requirement for a C8 oil filter change because conventional “strap-type” oil filter tools usually will not work. Otherwise, the filter change procedure is the same as for a C7. The filter choices are the same, too. Remove the old filter, clean the filter mount, prefill the new oil filter and wipe a little oil or grease on the filter gasket. Install the new filter and tighten 3/4-one turn.
Once the oil and filter changes are complete, reverse the jacking procedure discussed earlier, then set the rear of the car back on the ramps. Then, remove the front wheel chocks and reinstall the rear underbody deflector panel.
Remove the oil fill cap. The oil capacity of the LT2 including the filter is 7.5-qt, so subtract from 7.5-qt the amount of oil used to prefill the filter, then add that much Driven DI40 (just over 7-qt.) to the engine through the oil filler. Replace the cap. If you are more comfortable with absolute conformity to your C8s warranty, use Mobil 1 0W40 ESP

Warm the oil to 175°F either with a road test or a long idle time. Park on a level surface and leave the engine running at idle, then check the oil. It should be at or near the top of the crosshatched portion of the dipstick. If that’s where the level is, you’re done. 

C6-C8 Corvette Dry Sump Oiling System Service

Source: Zip Corvette Parts

8067 Fast Lane | Mechanicsville, VA 23111 | (800) 962-9632

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One Comment

  1. Damian

    The C8 2021 manual, page 239, states “… If the oil is below the cross-hatched area at the tip of the dipstick, add 1 L (1 qt) of the
    recommended oil …”

    You state :The very bottom of the crosshatched section is the one-quart low mark. Add a quart of oil when the oil level is at or below that.”

    Going with the manual statement it seems logical that if the level is below the crosshatched area, then adding 1 qt of oil is a good idea. Given the C8 can take more oil than 7.5 qts, adding the full quart seems logical.

    Can you clarify how your statement (specifically “bottom of crosshatch”) relates to the manual “specifically “below the bottom crosshatch)?

    Additionally, if you have time to expand the article, I would like to know where the oil reads when it is “full” at 7.5 quarts and where it reads after additional oil is added when the car it tracked.

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