Lower engine costs

[saturn13]

When does there have to be a new engine? The engines have seals. If there are anything that can be repaired internally hire a FIA inspector and to watch and certify nothing has been done to increase performance and put seals back on the engine. Does a burned piston destroy the engine? Send to factory for repairs or done at the teams shop using factory certified parts. Run on dyno to show the inspector that there is no hp gain. Would not count against the 5 engine rule. Install new piston sleeves maybe.
Refueling may be needed with a simple alternative engine. It would not have the efficiency of the hybrid engines. Inycar does ok doing this and limiting RPM to 12,000.

[Jolle]

When does there have to be a new engine? The engines have seals. If there are anything that can be repaired internally hire a FIA inspector and to watch and certify nothing has been done to increase performance and put seals back on the engine. Does a burned piston destroy the engine? Send to factory for repairs or done at the teams shop using factory certified parts. Run on dyno to show the inspector that there is no hp gain. Would not count against the 5 engine rule. Install new piston sleeves maybe.
Refueling may be needed with a simple alternative engine. It would not have the efficiency of the hybrid engines. Inycar does ok doing this and limiting RPM to 12,000.

Not having a cheap engine is just a choice. You can have a cheap 1000 hp engine without problem (just bolt a big turbo on something made of iron), but that not what the fia and the engine constructors wanted.
In the last turbo era Porsche made around 30 engines for the whole 4 years McLaren used the TAG brand. Just by rebuilding them over and over again.

This current configuration with, superb drivability, efficiency (close to 50%) and durability, is very usable (for the first time) road car/truck technology. I can see Mercedes use a MGU-H on a city bus within the next ten years

[gruntguru]

The five engine rule is designed to encourage the maker to produce a more reliable PU. Allowing exceptions would complicate things and penalize teams that build reliable engines that require no repairs while encouraging design and operation closer to the ragged edge.

[Tommy Cookers]

.....This current configuration with, superb drivability, efficiency (close to 50%) and durability, is very usable (for the first time) road car/truck technology. I can see Mercedes use a MGU-H on a city bus within the next ten years

existing types of (more-complete-expansion) engine already made in millions are far better suited to road car use ie at partial powers
and the hybrid thing benefits all types of engine

the current F1 engine is an engine type that gives the remarkable efficiency only at high % powers
emulating the 1950s aircraft engine that recovered without cost in fuel or crankshaft power 6% of 50% power but 18% of 100% power
and it relies on a 'superfuel'
and benefit in cars would be contingent on downsizing beyond levels currently experienced by the market

the best road application would seem to be the truck or long-distance bus

[Jolle]

.....This current configuration with, superb drivability, efficiency (close to 50%) and durability, is very usable (for the first time) road car/truck technology. I can see Mercedes use a MGU-H on a city bus within the next ten years

existing types of (more-complete-expansion) engine already made in millions are far better suited to road car use ie at partial powers
and the hybrid thing benefits all types of engine

the current F1 engine is an engine type that gives the remarkable efficiency only at high % powers
emulating the 1950s aircraft engine that recovered without cost in fuel or crankshaft power 6% of 50% power but 18% of 100% power
and it relies on a 'superfuel'
and benefit in cars would be contingent on downsizing beyond levels currently experienced by the market

the best road application would seem to be the truck or long-distance bus

I disagree, about the long distance bus/truck application. The constant accelerating and braking, like a racing car on a track, looks like what a city bus or parcel delivery truck in a big city does. Smart energy recovery systems like the MGU-K and MGU-H (they are turbo diesels 99% of the time) will save a lot of energy. Acceleration is almost always 100% of the power, just like a racing car, the weight ratio's are just a bit different.

for a long distance truck or bus a small engine a recovery system wouldn't be as helpful. A boost in the form of secondary E-motor would be a good application, without the generator.

[Turbo]

No Cheap Engines. If you can't afford F1 get out.