Engine Paints

Clear coats over engine paint

Why ordinary clear lacquer doesn't belong on an engine, the three cases where a clear is the right call, and the one clear that is rated for the heat.

Updated 2026-09-18

On this page
  1. The case against
  2. Where a clear is right
  3. Clears rated for heat
  4. Sources
  • Ordinary clear lacquer is rated to 80°C. An engine's coolant runs hotter than that.
  • Some enamel makers forbid overcoating altogether.
  • Even a matched engine clear is rated lower than the colour beneath it.
  • A clear earns its place over a metallic, on bare brackets, and where petrol is the threat.

The case against

The argument comes from the data sheets and rests on three figures.

Ordinary clear lacquer is an 80°C product. Hycote's acrylic clear is rated to 80°C, and so is its Petrol Resistant Lacquer. The same company rates its engine enamels at 140°C for gloss black and 300°C for aluminium and matt black. Lacquer over enamel gives you the enamel's colour and the lacquer's heat limit. A thermostat opens somewhere in the 80s, so anything bolted to the engine that carries coolant is already past what the lacquer is rated for.

The enamel's maker may forbid it. Hycote's engine enamel sheet lists, under where not to use the product, surfaces that will need overcoating with a different coating. The enamel is meant to be the finish.

A matched clear still lowers the ceiling. VHT's Engine Metallic is rated at 650°F, which is 343°C, intermittent. The clear VHT recommends over it, SP145 Engine Clear, is listed at 550°F, or 288°C, and so is the matching primer. Buy the system exactly as sold and the colour coat is the toughest layer in it. The primer below and the clear above both give up about 55°C sooner.

It is also worth asking what a clear is for. Hycote's acrylic finishes contain ultraviolet absorbers. On bodywork, that is the job: the clear takes the sunlight so the colour doesn't fade. Under a closed bonnet there is little sunlight to take. What you are left with is one more layer that can lift, and two coatings to strip at the next rebuild.

Where a clear is right

There are three cases.

The first is over a metallic, when the maker offers a matched clear. VHT lists SP145 as optional over Engine Metallic. The price is the lower rating described above. On a metallic part that lives somewhere cooler than the block, that can be a fair trade.

The second is bare metal that needs protecting and will never be painted a colour. Hycote describes its Petrol Resistant Lacquer as suitable on bare metallic surfaces where corrosion resistance is wanted. Brackets, linkages and bare alloy castings are the obvious candidates, provided they stay cool.

The third is where petrol is the threat and heat isn't. That lacquer exists because fuel strips ordinary finishes, and its stated purpose is protecting the paint on motorcycle tanks. In most engine bays the parts nearest the fuel are well away from the exhaust. For a tank, a filler neck or a bulkhead panel, 80°C is plenty.

Hycote also lists flexible plastic under where not to use it.

Clears rated for heat

There are fewer than the shelf suggests.

Among the products we have data sheets for, one clear carries a rating that means anything on an engine: VHT's SP145 Engine Clear, the third can of the VHT Engine Enamel system, listed at 288°C. That matches the enamel it was designed to go over and sits below the 343°C Engine Metallic.

Everything else a UK motor factor sells as clear lacquer is a bodywork product. Hycote's sheets are explicit: 80°C, for use over primers and acrylic finishes, on metal and rigid plastic.

The shop also lists very high temperature clears sold for exhaust work, such as E-TECH's XHT lacquer. Treat those like any very high temperature coating: read the maker's rating and its cure instructions before trusting it over a colour coat from a different brand.

See the clear lacquers in the shop.

Sources

In the shop

All 10 clear lacquers