Is it okay to have half a tank of 91 and fill it up with 95? asking for a friend

Is it okay to have half a tank of 91 and fill it up with 95? asking for a friend

pic unrelated

it depends on the engine senpai.
On the FSI and TFSI engines from VAG it is usually recommended to go atleast 3/4 91 and 1/4 95. Preferably to go all 95.

Diesels of old used to have 1-2 litres of petrol for every diesel fill up during winter times.

But to go half 91 half 95 is just retarded. You wont be getting anything out of it.

my car is a shitty old one and doesnt run as smooth anymore. 95 costs only about 8 cents more per litre in my country so I thought I would give it a go but I wanted to ask you guys, the experts first. Half a tank is a bit of a poor analogy desu but what I mean is basically I dont want to have to run it dry to try out 95 so is it okay if theres say a couple of litres left in the tank?

Depends on the engine senpai.
If its a small engine then wether you put 91 or 95 it doesnt mean shit. However, if you got a larger engine and you put 91, you will feel a loss of power.

You can mix them however you want, but on a small engine the 95 petrol is useless.

There are many things that make an engine go smooth, and the quality of the petrol is on the bottom of the list.

Consider using a different oil, either a more expensive brand, or maybe just change the viscousity alltogether. Clean the injectors.
Stuff like that.

what kind of petrol is 91? we dont have them here, only 95 and 98

its a carbed peice of shit from the 80s. the oil has been changed in the last 1000 ks and I heard that higher octain can help reduce carbon buildup and the like which is something I would like to achieve.
heres a pic so you know what I mean
1984 ford laser (mazda 323)

by 'here' I assume you mean america?
in nz we have 91 octane which is regular for us and costs about $2 NZD per litre depending on where you go and most cars run fine exclusively on 91 seeing as its slightly cheaper. 95 is only 8 - 15 cents more expensive and usually is used by gas guzzlers or older cars that were designed for it. 98 isnt sold at every station because its usually only the enthusiasts and the like that run it in their cars but you can find it all the time at bp for whatever reason.

My old mate had one of those with a big fuckoff ding in the drivers side front fender

"How'd you manage that?"

"I kicked it"

I use 95 cuz 91 tanks aren't kept as clean, and I have a timing advance that'll ping to fuck on 91.

the previous owner drove it into the fence in their driveway a few times.
theres one on either side

Damn.
You can learn a lot from owners manuals eh. I still haven't read mine cover to cover yet. It's a lot more reading than some Japanese car

With all due respect user, but the necessary ammount of 95 petrol required for a significant cleaning might be worth more than the car itself.

Technically you heard right, but cleaning the pipes would be more efficent.

Or just buy a more modern car, if you want something smoother. Heard you amerifats have cars for insultingly low prices.

I live in nz and this is my hand-me-down daily. she spits white smoke when shes cold and black shit comes out the tailpipe at high rpm so anything cleaner is a significant improvement

if you still want to save the shitbox, heres something for you:
black shit coming out of tailpipe means that you need to clean the injectors asap.
white smoke coming out of tailpipe means you are not using the correct engine oil.

If I were you Id just a buy a 500 euros Corsa C and get on with it. Or a newer Mazda 323.
Coworker bought a 2001 Mazda 323 BG for just 995 euros. 1.5L petrol that develops 98 bhp and he is quite happy with it.

Or get yourself a Passat B4 or Audi A4 B5, for about the same 1000 euros or less.

bro I have no intention of buying a new car until I have at least five grand and this thing is indestructible and has no problems at the present time so theres no point. the only thing I want to do is help the smoke problem if I can. thanks for the advice tho

A 2001 323 would have been a BJ, not a BG.

If you're asking if it's safe to mix fuel with different octane ratings, then yes its perfectly fine.

Put thicker oil in it
Get a thing of injector cleaner from superchips when it's on sale and dump that in when you're down to about 1/4 tank
Run 95 anyway, won't do it any harm
Run the fuckin thing into the ground. Just don't tell judith collins your car is more than 10 years old.

what would thicker oil do?
injector cleaner sounds like a good plan though I might look into that
>run it into the ground
planning on it
finally the answer I was looking for

it's fine. you might hear a ping noise and it's just an early combustion in the engine. stop wasting money on preemo stuff if your car doesnt need it

One step up in oil thickness is better for older engines where internal engine parts have worn from use. Keeps the oil where it should be and things running smooth.
The most pertinent thing in your case is that thicker oil is less likely to seep past piston rings into the combustion chamber, reducing smoke.

also injector cleaner and seafoam in your top end should kill most of that carbon gunk; its gonna be a show, though

You'd end up with 93 octane fuel if you did a half and half mix of 91 and 95. Likewise, if you had a quarter tank of 91 and filled up with 95, you'd be at 94. Whether that'll work or help depends on the engine which is why you shouldn't start threads with such little information.

Octane probably isn't your engine's main problem.

Just 93 innit