Follow Schedule 1 if your car is mainly operated under one or more of the following conditions:.
When most trips are less than 4 miles (6 kilometers)
When most trips are less than 10 miles (16 kilometers) when outside temperatures are below freezing.
When the engine is at low speed most of the time (as in stop-and-go traffic).
When operating in dusty areas.
Follow Schedule 2 only if none of the driving conditions specified in Schedule 1 apply.
The 1991 Corvette has an Engine Oil Life Monitor. This monitor will show drivers when to change their oil - usually between 3,000 miles (5,000 km) and 7,500 miles (12,500 km) since the last oil change. Under severe conditions the indicator may come on before 3,000 miles (5,000 km). Never drive your vehicle more than 7,500 miles (12,500 km) or 12 months whichever occurs first, without an oil change.
The system won’t detect dust in the oil. If you drive in a dusty area be sure to change your oil every 3,000 miles (5,000 km) or sooner if the CHANGE OIL light comes on. Remember to reset the Oil Life Monitor when the oil has been changed. See “GM Oil Life System" (at the bottom of this page) for more information on resetting the system.
Explanation of Scheduled Maintenance Services:
1.) Engine Oil and Filter Change:
Use only API Service SG Energy Conserving II oils of the proper viscosity.* The engine requires a special oil meeting GM Standard GM4718M. Oils meeting this Standard may be identified as synthetic, and should also be identified as API Service SG. However, not all Synthetic API Service SG oils will meet this GM Standard. You should look for and use only an oil that meets GM Standard GM4718M.
2.) Chassis Lubrication:
Lubricate the transmission shift linkage, parking brake cable guides, underbody contact points and linkage. Lubricate the front suspension.
3.) Engine Accessory Drive Belt Inspection:
Inspect the belts for cracks, fraying, wear and proper tension. Replace as needed.
4.) Cooling System Service:
Drain, flush and refill the system with new or approved recycled coolant conforming to GM Specification 1825M. Keep coolant at the proper mixture as specified. This provides proper freeze protection, corrosion inhibitor level and engine operating temperature.
Inspect hoses and replace if they are cracked, swollen or deteriorated. Tighten screw-type hose clamps. Clean the outside of the radiator and air conditioning condenser. Wash the pressure cap and neck.
To help ensure proper operation, we recommend a pressure test of both the cooling system and the pressure cap.
5.) Transmission Service:
For manual transmissions, the fluid doesn't require changing.
For automatic transmissions, change both the fluid and filter every 15,000 miles (25,000 kilometers) if the vehicle is mainly driven under one or more of these conditions: heavy city traffic where the outside temperature regularly reaches 90°F (32°C) or higher, in hilly or mountainous terrain. Uses such as found in taxi, police or delivery service. If you do not use your vehicle under any of these conditions, change the fluid and filter at 100,000 miles (166,000 kilometers).
6.) Spark Plug Replacement:
Replace spark plugs with the proper type.
7.) Spark Plug Wire Inspection:
Inspect for burns, cracks or other damage. Check the boot fit at the coils and at the spark plugs. Replace the wires as needed.
8.) Air Cleaner Filter Replacement:
Replace every 30,000 miles (50,000 kilometers) or more often under dusty conditions. Ask your local dealership for proper intervals based on individual driving conditions.
9.) Fuel Tank, Cap and Line Inspection:
Inspect the fuel tank, cap, and lines (including fuel rails and injection assembly) for damage and leaks. Inspect fuel cap gasket for an even filler neck imprint or any damage. Replace parts as needed. Periodic replacement of the fuel filter is not required.
Owner Inspection & Service Items
At Each Fuel Fill
NOTE: It is important for you or a service station attendant to perform these underhood checks at each fuel fill.
Engine Oil Level Check:
Check the engine oil level and add the proper oil if necessary.
If you have a ZR-1 you should check your engine oil when the engine is cold.
Engine Coolant Level Check:
Check the engine coolant level and add the proper coolant mixture if necessary.
Windshield Washer Fluid Level Check:
Check the windshield washer fluid level in the windshield washer tank and add the proper fluid if necessary.
At Least Once a Month
Tire Inflation Check:
Make sure tires are inflated to the correct pressures specified on the Tire-Loading Information Label located on the rear edge of the driver door.
At Least Once A Year
Key Lock Cylinder Service:
Lubricate the key lock cylinders.
Body Lubrication Service:
Lubricate all body door hinges. Also lubricate all hinges and latches, including those for the hood, rear compartment, console door and any folding seat hardware. More frequent lubrication may be required when exposed to a corrosive environment.
Starter Switch Check:
CAUTION: When you are doing this check, the vehicle could move suddenly. If it does, you or others could be injured.
Before you start, be sure you have enough room around the vehicle.
Firmly apply the parking brake and the regular brake. (NOTE: Do not use the accelerator pedal, and be ready to turn off the engine immediately if it starts.)
On automatic transmission vehicles, try to start the engine in each gear. The starter should work only in PARK (P) or NEUTRAL (N). If the starter works in any other position, your vehicle needs service.
On manual transmission vehicles, put the shift lever in NEUTRAL (N), push the clutch down halfway and try to start the engine. The starter should work only when the clutch is pushed down all the way to the floor. If the starter works when the clutch isn’t pushed all the way down, your vehicle needs service.
Steering Column Lock Check:
While parked, and with the parking brake set, try to turn the ignition key to OFF in each shift lever position.
With an automatic transmission, the key should turn to LOCK only when the shift lever is in PARK (P).
With a manual transmission, the key should turn to LOCK only when the shift lever is in REVERSE (R).
On all vehicles, the key should come out only in LOCK.
Parking Brake and Automatic Transmission PARK (P) Mechanism Check:
CAUTION: When you are doing this check, your vehicle could begin to move. You or others could be injured and property could be damaged. Make sure there is room in front of your vehicle in case it begins to roll. Be ready to apply the regular brake at once should the vehicle begin to move.
Park on a fairly steep hill, with the vehicle facing downhill. Keeping your foot on the regular brake, set the parking brake.
To check the parking brake’s holding ability: With the engine running and transmission in NEUTRAL (N), slowly remove foot pressure from the regular brake pedal. Do this until the vehicle is held by the parking brake only.
To check the PARK (P) mechanism’s holding ability: With the engine running, shift to PARK (P). Then release the parking brake followed by the regular brake.
Underbody Flushing Service:
At least every spring, use plain water to flush any corrosive materials from the underbody. Take care to clean thoroughly any areas where mud and other debris can collect.
Dealership Inspection & Service Items
At Least Twice A Year
Steering and Suspension Inspection:
Inspect the front and rear suspension and steering system for damaged, loose or missing parts, signs of wear or lack of lubrication. Inspect the power steering lines and hoses for proper hook-up, binding, leaks, cracks, chafing, etc.
Tire and Wheel Inspection:
Inspect the tires for uneven wear or damage. If there is irregular or premature wear, check the wheel alignment. Inspect for damaged wheels.
Exhaust System Inspection:
Inspect the complete exhaust system. Inspect the body near the exhaust system. Look for broken, damaged, missing or out-of-position parts as well as open seams, holes, loose connections or other conditions which could cause a heat build-up in the floor pan or could let exhaust fumes into the vehicle.
Rear Axle Service:
Check the gear lubricant level in the rear axle and add if needed. A fluid loss may indicate a problem. Check the axle and repair it if needed.
Brake System Inspection:
Inspect the complete system. Inspect brake lines and hoses for proper hook-up, binding, leaks, cracks, chafing, etc. Inspect disc brake pads for wear and rotors for surface condition. Inspect other brake parts, including calipers, parking brake, etc. You may need to have your brakes inspected more often if your driving habits or conditions result in frequent braking.
NOTE: A low brake fluid level can indicate worn disc brake pads which may need to be serviced. Also if the brake light stays on or comes on, something may be wrong with the brake system. If your anti-lock brake system warning light stays on, come on or flashes, something may be wrong with the anti-lock braking system.
GM Oil Life System
Your vehicle has a computer that lets you know when to change your engine oil. This is not based on mileage, but on engine revolutions and engine operating temperature. When the computer has calculated that the oil needs changing, the GM Oil Life System will indicate that a change is necessary. The mileage between oil changes will vary depending on how you drive your vehicle -- usually between 3,000 miles (5 000 km) and 10,000 miles (16 000 km) since your last oil and filter change. Under severe conditions, the system may come on before 3,000 miles (5 000 km). Never drive your vehicle more than 10,000 miles (16 000 km) or 12 months (whichever occurs first) without an oil change. Use engine oil meeting the GM Standard GM4718M.
The system won’t detect dust in the oil. So, if you drive in a dusty area, be sure to change your oil and filter every 3,000 miles (5 000 km) or sooner if the CHANGE OIL SOON message appears. Remember to reset the system whenever the oil is changed.
How to Reset the Change Oil Soon Message
To reset the CHANGE OIL SOON message after an oil change, do the following:
1. Turn the ignition to ON and with the engine off.
2. Press the TRIP button so the OIL LIFE percentage is displayed.
3. Press RESET and hold for two seconds. OIL LIFE REMAIN 100% will appear.
DISCLAIMER: While Corvsport.com makes every effort to ensure that this information is complete and accurate, you should always consult the manufacturer of your vehicle if you have a specific issue or question.
1991 Corvette Fluids/Lubricants
Engine Oil: Use SAE 5W-30. However, you can also use SAE10W-30 if it’s going to be 0 F (-18C) or above. The engine requires a special Engine Oil meeting GM Standard GM4718M. Oils meeting this Standard may be identified as synthetic, and should also be identified with the American Petroleum Institute Certified For Gasoline Engines starburst symbol. However, not all Synthetic API oils with the Starburst symbol will meet this GM Standard. You should look for and use only an oil that meets GM Standard GM4718M.
Engine Coolant: 50/50 mixture of water (preferably distilled) and GM Goodwrench DEX-COOL or Havoline DEX-COOL (orange-colored, silicate-free) antifreeze
conforming to GM Specification 6277M.
Coolant Supplement Sealer: GM Part No. 3634621 or equivalent with a complete flush and refill.
Hydraulic Brake System: Delco Supreme 11 Brake Fluid (GM Part No. 1052535 or equivalent DOT-3 brake fluid).
Hydraulic Clutch System: Hydraulic Clutch Fluid (GM Part No. 12345347 or equivalent).
Parking Brake Cable Guides: Chassis lubricant (GM Part No. 1052497 or equivalent) or lubricant meeting requirements of
NLGI Grade 2, Category LB or GC-LB.
Power Steering System: GM Synthetic Power Steering Fluid (GM Part No. 12345866 or 12345867 or equivalent).
Manual Transmission: Manual Transmission Fluid SAE 5W-30 (GM Part No. 1052931 or equivalent).
Key Lock Cylinders: Multi-Purpose Lubricant, Superlube (GM Part No. 12346241 or equivalent).
Manual Transmission Shift Linkage: Chassis lubricant (GM Part No. 1052497 or equivalent) or lubricant meeting requirements of NLGI Grade 2, Category LB or GC-LB.
Clutch Linkage Pivot Points: Engine Oil
Floor Shift Linkage: Lubriplate Lubricant aerosol (GM Part No. 12346293 or equivalent) or lubricant meeting requirements of NLGI Grade 2 Category LB or GC-LB.
Chassis Lubrication: Chassis lubricant (GM Part No. 1052497 or equivalent) or lubricant meeting requirements of NLGI Grade 2, Category LB or GC-LB.
Rear Axle (Limited Slip Diff.): Axle Lubricant (GM Part No. 12345977) and 4 ounces (118ml) of Limited-Slip Differential Lubricant Additive (GM Part No. 1052358 or equivalent) where required.
Windshield Washer Solvent: GM Optikleen@ Washer Solvent (GM Part No. 1051515) or equivalent.
Hood Latch Assembly, Secondary Latch, Pivots, Spring Anchor and Release Pawl: Lubriplate Lubricant Aerosol (GM Part No. 12346293 or equivalent) or lubricant meeting requirements of NLGI Grade 2, Category LB or GC-LB.
Hood and Door Hinges: Multi-Purpose Lubricant, Superlube (GM Part No. 12346241 or equivalent).
Weatherstrip Conditioning:Di-Electric Silicone Grease (GM Part No. 12345579 or equivalent).
Recommended oil, transmission, and all other fluids should meet/exceed the minimum requirements listed above. Current API ratings on oil and transmission fluids exceed those listed at the time the above information was originally published.