Frequently Asked Questions answered by individual members of Natural Glass Corvette Association.

Winter Storage and High Flow Air Filters

The following is a series of questions and answers posted by club members in an effort to help share information with each other. Many of the answers are based on the personal opinions of the individual member, and may or may not produce the results desired by the member who posed the question. Therefore the posting of these answers is not an endorsement by NGCA of the opinions expressed therein. We recommend that you conduct further research and consult a qualified GM expert before attempting to perform any of the suggested techniques or procedures listed below.

Question: How to properly store the car over the winter?

a. Battery care.

b. Proper fuel care.

c. Oil and other fluid preparation.

d. Tires.

e. Other suggestions.


1. Change all fluids before cold weather storage. On the Vette, that would include engine oil and every other year, the rear end fluid. Fill fuel tank. Add one bottle of "Sta-bil" (boat yard stuff).

2. Leave the batter connected, but connect a Battery Tender (cheep, 49 bucks at any motorcycle shop). This will keep a "float charge" on the battery and keep it in top condition.

3. Either get the tires off the floor, or pump up tire pressure to 40 PSI.

4. Place a bag of anti-mildew compound in the car - - I suspend it in a bag hung from the steering wheel.

5. Once a month, start it up, and run engine till oil temp gets to 220 degrees, hot enough to boil off any condensation in the crankcase.

6. On Spring restart.... adjust tire pressure to specs, check all fluid levels, disconnect battery tender, remove and discard mildew bag, fire it up and drive!

Answer Submitted by – A.E.

1) Disconnect battery when storing. Remove if stored area isn't above 55 degrees.

Connect a trickle charger (Battery Tender) about a month before ready to use Vette.

Last season I purchased an Optima Red Top battery.

It's a get battery rather than liquid content that holds a charge for a long time.

Also since it doesn't gas off like standard batteries when charging. So no odor is noticed in C-3s.

2) Add Fuel stabilizer such as Sta-bil. Fill tank to top. Run car Take a short ride to circulate stabilizer.

3) Change oil and filter BEFORE storing vehicle.

4) Add 5lbs or so extra air in tires when storing.

5) Oil filters. I use Amsoil Filters in my everyday vehicles.

Due to changing my synthetic oils every 7K miles or so which is twice a year for me. Amsoil filter can go 12,500 miles according to Amsoil.

In the Vette I use an AC or Amsoil.

I only drive her around 2K a year.

I use synthetic oil in the Vette too and change it once a year before storage.

Some say over the winter they start the car and run it for 20 minutes or so on occasion over the winter. I've also read it's better to just leave it alone over the winter.

That's your decision. Another tip depending on how it's stored is to add Irish Spring soap bars to the interior to eliminate a musty odor and to plug tailpipes for condensation.

I store in my garage with heat so I don't need to follow the last two techniques.

Answer submitted by – J.B.

I recommend reading this article from the Corvette Action Center.

Answer submitted by – D.W.

The question comes down to complete storage or just "put away" for the winter. Complete storage means the car can't be just started up in the spring and driven around. As a note, I never stored my cars but kept them in running condition and actually tried to run them every 2-3 weeks in the winter.

The battery should be disconnected from the vehicle if possible. With the later generations starting with C4, disconnecting the battery will result in the loss of stored data such as radio & memory presets and more importantly, ECM & other computer settings.

The latter results in the computers having to "relearn" when the car is started up. A trickle charger such as the one sold by the NCM is an excellent alternative to disconnection but I would not just hook it up and leave it. Rather every few weeks connect it till the battery is fully charged. Also keep an eye on fluid level, something that is often overlooked. Remember that on the newer generations, the computers, vats, memory & entry systems, continue to pull current even while parked so the batteries will die if left. One of the best ways to ensure long battery life is to make sure that you put the charger on the battery and bring it up to full charge before you crank the car after sitting for a long time. When my cars saw limited use in winters, I always hooked up the charger before cranking the car and I got very good useful lives from the batteries.

A fuel treatment such as Sta-bil should be added to the fuel tank and the engine run to make sure the treatment has gone thru the fuel delivery system. This will prevent the gas from evaporating in areas and leaving a varnish deposit. It's a must do and recommended year round for cars that get limited use.

I always changed the oil in the fall when the car went into semi hibernation and used slightly thinner oil so that I could start the car and run it occasionally during the winter. Every 3 years antifreeze should be changed. I changed mine more frequently in the midyears because in the summer I ran a water/af mix of 75/25. For winters I added AF or just flushed and added a 50/50 mix.

I have heard of people saying that the car should be stored with the tires off the ground or not on concrete. I never had a problem with just parking the car but I did start and drive the car on a limited basis during the winter so it wasn't a problem. I would suggest parking with the tires on some carpet remnant or some kind of mat, cardboard just to keep them off of concrete which can allow moisture to accumulate.

To put away completely, many people start the car and while idling pour a small amount of oil into the carb or run it through the fuel system until there is smoke from the exhaust. That coats the engine interior parts with a thin layer of oil and reduces possible rusting or deposits. Then rags should be stuffed in carb intake and rag and steel wool in the exhaust (discourages mice) as well as blocking moisture. Just don't forget to remove before starting. A breathable car cover is a good idea and many people use bags of desiccant to control moisture inside the car.

Answer submitted by – R.L.

Question: I read recently that High Flow air filters, like K&N filters, provide little or no advantage on street cars and in fact can cause serious problems if not properly maintained (Pat Goss in the NCOA Newsletter). Is this true?


In regard to K&N air filter----first recognize a Corvette is not a Street Car; it is a high performance sports car. That having been said, if you also change the air cleaner housing, or modify the stock housing, to permit more air intake into the filter housing, the K&N WILL increase HP. As far as maintenance, the K&N must be oiled. A dry K&N provides little filtering capability. An annual wash, dry and re-oil of the filter element does the trick. The air flow improvement of the K&N is most noticeable at higher RPMs (above 5,000.) I have K&Ns on the Vetter, Scooter, Boat and Caddy. HP gains of +15 to 20 HP with a free flowing air filter housing + K&N + free flow exhaust (Corsa) are dyno documented for C-5 Vettes.

Answer submitted by – A.E.

I have received and read Pat Goss' column concerning the K&N type filter. I understand Pat Goss' point and would not disagree concerning a stock engine. Also GM has potential warranty and other issues that they are trying to avoid, thus they don't want modifications to their cars if the owner expects GM to warranty the car. The exception being GM licensed / sold parts installed by their dealers.

Answer Submitted by – D.W.

The air filter in question has the advantage of less air restriction and better air flow to the intake. In order to provide the reduced restriction, comes a slight reduction in filtering ability. Whether the filter is used on the street or in racing applications has little to do with its advantages or disadvantages.

Improper maintenance of any filter will only serve to reduce the amount of air entering the intake system and a reduction in engine efficiency as well as fuel economy will be the results. An improperly maintained system will reduce the amount of air as well as any impurities from entering the intake. However, if the intake becomes totally clogged, it is conceivable the filter element will be damaged allowing unfiltered air to enter. This would be true with both stock as well as after market systems. There is no evidence presently available that supports the belief that the low restriction air intake system will cause great harm to a street or competition engine.

There are many claims for hp increases with these low restriction system. However, the real gains these system provide, have more to do with the temperature of the air rather then the just the reduced restrictions. Many of these systems change the air flow from the warm air in the engine compartment to cooler air from outside the engine compartment. The cooler air has a higher density then the warm air and as such will allow a denser fuel air charge to enter the intake. It is the denser air fuel mixture that provides the increased power and not just the lower air restriction.

Answer submitted by – M.H.

Other Frequently Asked Corvette Questions

The answers may reflect personal opinions of individual members and are not an endorsement by NGCA. Always make sure to consult a qualified GM expert and conduct proper research first.

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