feat(balance): gasoline engines can burn alcohol, V8 and V12 engines in general require higher-quality fuel

[chaosvolt]

Checklist

Required

• I wrote the PR title in conventional commit format.
• I ran the code formatter.
• I linked any relevant issues using github keyword syntax so it can be closed automatically.
• I have committed my changes to new branch that isn't main so it won't cause conflict when updating main branch later.

Optional

Purpose of change

I mentioned in #5749 that allowing gasoline engines to run biodiesel but not regular diesel was a bit of an oddball decision, with alcohol arguably being the better choice for them (as @yay855 initially did in their PR before being nudged to switch it to biodiesel).

Describe the solution

1. Changed the gasoline_engine abstract to allow ethanol, denatured alcohol, and methanol instead of biodiesel. As noted in discussion of feat(content): Biodiesel Fuel for Gasoline Engines #3716 the worry was that easy access to putting booze in your gasoline engine would make diesel engines obsolete. The main counterpoints are that ethanol still takes time and resources to set up (made arguably a bit less roadblocked but no less of a logistical hassle by feat(content): add clay and copper retorts for craftable DISTILL quality 1 #4977), while diesel engines have the even easier to produce option of lamp oil to run off of. It was additionally pointed out that ethanol has a fuel value of 15.6 compared to biodiesel's 29.6, so if anything if the concern is making diesel engines stay relative why would you give it a fuel option that has twice the effectiveness of the more obvious choice?
2. Additionally added those three fuel options to the gas_turbine_engine abstract, maintaining the glorious tank and heli engine superiority over puny gasoline and diesel engines.
3. Per Coolthulhu's suggestion, V8 and V12 engines were given stricter fuel requirements for balancing purposes, losing access to alcohol (gasoline engines) and lamp oil/motor oil (diesel engines). Per his suggestion, turbine engines retain the ability to eat whatever they like since they're low-efficiency.
4. Updated description entries accordingly.

Describe alternatives you've considered

1. Adding E85 fuel for more realism points and/or a way to stretch out the player's supply of gasoline without going full dorf mode like using pure alcohol would entail.
2. Rigging it so we can power engines with just vodka and other drinkable alcohols for the lulz.

Testing

1. Checked affected files for syntax and lint errors.
2. Load-tested in compiled test build.
3. Spawned a regular car, confirmed it lets me switch it to run off denatured alcohol.
4. Spawned a big-ass V8 truck, confirmed it only accepts gasoline and avgas, and the engine description is different.

Additional context

[RoyalFox2140]

A year ago Kheir shot this down, so let's see how it goes this time. I'll ask and we'll have to discuss it more.

[yay855]

Yes, I tried to do the same thing and it didn't get approved. Chaos's reasons are sound, at least.

[chaosvolt]

Adding my musings from the discord here:

[blot-runner]

Adding my musings from the discord here:

You seem to focus exclusively on ethanol and denatured alcohol in your comparison. But methanol is super easy to produce in the game. No still, no fermenting, no rare tools or components al all, no books to search for, all you need is wood, water, clay retort, brazier and fire, and you're mass-producing fuel. The only real gateway here is Cooking 4, as opposed to 2 for the lamp oil, but that can be trained quite fast (I think it took me a day of game time). It does take twice the time to produce the same amount, comparing to the lamp oil, but the latter requires you to at least search for a pot or other proper cooking implement, not to mention hunting, fighting zombies or scavenging for the necessary fats.

[chaosvolt]

No still

It does require distilling quality 1 which a clay retort provides, same as denatured alcohol. You're right though, wood does make the comparison more complicated and makes it possible to skip out on the fermentation. I do still feel that this is more reasonable than lamp oil to be honest?

Plus we really should not have added biodiesel to gasoline engines as an alternative to that, it makes it seem really weirdly inconsistent to allow one form of diesel but not factory-made ones.

[RoyalFox2140]

I am fine taking off biodiesel from gasoline engines unless a realism argument exists for biodiesel being used in a gasoline engine.

[chaosvolt]

That would work too I suppose. Any other devs we should ask for an opinion on the current PR proposal, or should I just make it a removal of gasoline engines running biodiesel?

[Coolthulhu]

Feels a bit weird IMO. Not as weird as biodiesel in gas engines, but still weird.

Blending would be more realistic, but wouldn't solve the gameplay issue of gas being non-renewable.
Is it really a huge deal if gas engines are non-renewable? It seems that the lamp oil diesel is the biggest outlier here, so rebalancing everything around that means more work than nerfing lamp oil.

I'd say that the best way to balance it would be to have lower level engines accept more fuel types, but have V12 only work with (av)gas for gasoline, and (bio)diesel for diesel. As far as I recall, gas turbines are inefficient, so it seems fine for them to be able to burn weird stuff.

[chaosvolt]

I'd say that the best way to balance it would be to have lower level engines accept more fuel types, but have V12 only work with (av)gas for gasoline, and (bio)diesel for diesel. As far as I recall, gas turbines are inefficient, so it seems fine for them to be able to burn weird stuff.

That works then. Does that mean we want V12 diesel to disallow lamp oil and motor oil?

Honestly if needed then just removing biodiesel from gasoline engines works too.

[blot-runner]

@RoyalFox2140

I am fine taking off biodiesel from gasoline engines unless a realism argument exists for biodiesel being used in a gasoline engine.

From what I was able to learn, it's the opposite - even stock diesel engines cannot run on pure biodiesel, you'll need AT LEAST 80% of the petrol diesel in the mix (pure biodiesel is still possible if the engine is modified to accept it). Taking into account the fact that one of the main problems is much higher viscosity than that of petrol diesel, I think the gasoline engine will die quite fast when fueled with any amount biodiesel (presumably, the injectors would be the first thing to go, but I'm no mechanic).

@Coolthulhu

I'd say that the best way to balance it would be to have lower level engines accept more fuel types, but have V12 only work with (av)gas for gasoline, and (bio)diesel for diesel.

I know that you're talking about gasoline/diesel engines and what I'm saying might be beyond this PR's scope, but - wouldn't it be nice to have steam engines accept liquid fuels too? All of them? I mean, as far as I know, they aren't really efficient, but their RL staple is "anything that burns is fuel" and it might provide an interesting alternative for lowtec runs.

As far as I recall, gas turbines are inefficient, so it seems fine for them to be able to burn weird stuff.

IRL they are the most efficient of the three (the best are >60% vs. ~55% for diesel and ~40% for gasoline engines, if the Wiki is to be trusted). IDK, I always thought the main balancing factor there was "like hell you're going to find one". Or is it just my luck?))

[chaosvolt]

To be fair, Coolthulhu likely meant they're inefficient more than they're wasteful unless you have a downright wacky deathmobile. They have decent efficiency in game terms if I recall, just their power is so high that their fuel use is just high overall as a result.

[blot-runner]

To be fair, Coolthulhu likely meant they're inefficient more than they're wasteful unless you have a downright wacky deathmobile. They have decent efficiency in game terms if I recall, just their power is so high that their fuel use is just high overall as a result.

Wait, you mean, there are people who don't build wacky deathmobiles?
Jokes aside, though, I've just checked combustion.json - gasoline engines, diesels and gas turbines are coded at 30%, 40% and 25% efficiency, respectively. For comparison, steam engines are 50% efficiency. 0_0
So, gas turbines are the least efficient, while steam engines are the most. Shouldn't it be the other way round?