Get the Best Engine Oil for Your Corvette

Castrol Syntec 20W-50
This engine oil contains the ZDDP additive required for older engines. Photo courtesy of Castrol

You have made a big investment in your Corvette, and the beating heart of your car is the engine. You want to take care of it in the best possible way, but there are a tremendous variety of engine oils out there - which should you use?

Basic Engine Oil Rules

  • Any Corvette built since 1989 needs the specific oil recommended by Chevrolet for your engine. Generally, this is 5W-30 synthetic oil, and GM specifically warns against using any other formulation, such as 10W-40 or 20W-50. For the last several years, GM has specified Mobil 1 5W-30 synthetic oil and filled every Corvette with that oil at the factory.
  • The owner's manual for the 2010 Corvette notes that all oil used in the Corvette must meet GM4718M standard, and be labeled as meeting the standard. See your owner's manual for your recommended type and grade of oil.
  • Any Corvette built before 1989 can use modern synthetic oils of the same weight as recommended for the car originally, but those engines are designed to be lubricated with oils containing Zinc Dialkyl DithioPhosphate (ZDDP).

About ZDDP

ZDDP used to be an ingredient in most engine oils. The zinc is deposited on bearing surfaces such as your cam and lifters over time, protecting the metal from wear. But ZDDP was eliminated from most motor oils to improve emissions control in the modern era.

The emissions issue is comparatively small: Some zinc and phosphorus from the ZDDP ends up in your catalytic converter and reduces its working life. ZDDP does not contribute to pollution, it just means you have to replace the catalyst after about 50,000 miles.

Here are your choices when it comes to ZDDP:

  • If you have a Corvette made from 1975-1988, you need to understand the trade-off between shortened life of your catalyst, which is easy to replace, or shortened life of your camshaft, which is hard to replace.
  • If your Corvette was made before 1975, you need ZDDP in your oil.

Several good synthetic oils contain the required concentration of ZDDP to protect older engines. Among these are Castrol Syntec 20W-50, Valvoline VR1, Royal Purple XPR, Red Line, Mobil 1 15W-50 and Amsoil Synthetic Premium Protection. Other oils may contain ZDDP, and will usually state the ZDDP concentration on the bottle.

Rebuilt Engines

If the engine in your car is not the original engine, use the oil that your engine builder recommends. With freshly-rebuilt engines, it is especially crucial that you follow the engine builder's instructions for break-in procedures, oil and filter selection, and driving limitations. Ask your engine builder before you introduce ZDDP or any additive product to your engine through the oil or the fuel.

Change Your Oil Filter, Too

Another key to good engine maintenance is your oil filter. You should replace your filter every time you change your oil. Modern oil filters flow better and filter better than their vintage counterparts. If your car is a 100-point showpiece, you'll want the original look, but if you plan to drive your car, get a modern filter on there every time. Good filter choices include the Mobil 1 filter, Fram PH3506, or the AC Delco PF46.

Get on a Schedule

The bottom line on lubrication is simple: use fresh oil on a regular basis to maintain your Corvette. Even if you're not driving your 'Vette much, the combustion by-products that end up in your motor oil turn into acids and eat away at your bearing shells. Change your oil at least every 3,000 miles or every 6 months no matter how many miles you've put on the car. A regular maintenance schedule helps keep your Corvette happy.

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