What octane for winter?

2001 ACR · Post by **2001 ACR** » Fri Dec 05, 2008 6:12 pm

I always put 93 octane fuel in my car in the summer months, but now that winter is here, and the temperature is below 0 Cel, is it best to go to a lower octane fuel? My engine runs really hard when it first starts up, and almost sounds like it is knocking. Would going to 87 octane help the engine run smoother?

Post by **racer12306** » Fri Dec 05, 2008 6:43 pm

More than likely not. Just run your normal gas grade.

2001 ACR · Post by **2001 ACR** » Fri Dec 05, 2008 6:59 pm

racer12306 wrote:More than likely not. Just run your normal gas grade.

So what CAN I do to get my car to start and run smoother in the winter? I hate hearing my engine knock.

03blackrt · Post by **03blackrt** » Fri Dec 05, 2008 7:03 pm

That 'knock' is piston slap.

When it gets cold out the clearence between the piston and cylinder wall increases. Once the engine warms up it should go away.

Donkeypuncher · Post by **Donkeypuncher** » Fri Dec 05, 2008 7:10 pm

During the winter I would imagine 87 octane is just fine. Before gas sky rocketed I used 93 year round, but especially for the 100+ degree weather. I would think 87 would be fine for winter, but I would run at least 89 or 91 on an r/t or acr just to be on the safe side, especially if you like to take it above 5k rpms regularly.

It's a good idea to drop down to 0w oil for the winter as well, more so if you live in a northern region. Also, redline water wetter is a good idea for all year round conditions. I was pleasantly surprised that my car ran better during all weather conditions with the stuff.

Adionik · Post by **Adionik** » Fri Dec 05, 2008 7:51 pm

Haha...you don't need to change octane. It's the oil that's giving you the piston slap.

Haganracing · Post by **Haganracing** » Fri Dec 05, 2008 8:32 pm

2001 ACR wrote:
racer12306 wrote:More than likely not. Just run your normal gas grade.
So what CAN I do to get my car to start and run smoother in the winter? I hate hearing my engine knock.

Turn the radio up

These 2.0 engines are noisy.

2001 ACR · Post by **2001 ACR** » Fri Dec 05, 2008 8:47 pm

Donkeypuncher wrote:During the winter I would imagine 87 octane is just fine. Before gas sky rocketed I used 93 year round, but especially for the 100+ degree weather. I would think 87 would be fine for winter, but I would run at least 89 or 91 on an r/t or acr just to be on the safe side, especially if you like to take it above 5k rpms regularly.

It's a good idea to drop down to 0w oil for the winter as well, more so if you live in a northern region. Also, redline water wetter is a good idea for all year round conditions. I was pleasantly surprised that my car ran better during all weather conditions with the stuff.

Forgive my ignorance, but what is redline water wetter?!? And can someone explain why 0w oil would prevent piston slap as opposed to 5w oil? I'm not used to driving in cold climates... I'm from Texas and now live in Kentucky where it stays below 0 C from December to April.

03blackrt · Post by **03blackrt** » Fri Dec 05, 2008 9:19 pm

Oil type has nothing to do with piston slap.

Donkeypuncher · Post by **Donkeypuncher** » Fri Dec 05, 2008 9:20 pm

Water wetter is just an additive for your coolant, during the summer it allows the coolant to dissipate heat much faster than a coolant/water mixture alone. My car seemed to warm up faster during the winter as well, but I couldn't say why it caused that.

0w specifies the weight of the oil, it means the oil is actually thinner at cold temperatures which allows for better lubrication when the engine is started at lower temperatures. It lubricates the piston rings, rods, and valves faster than a heavier 10w oil on colder starts since it's not as thick (think maple syrup vs. milk). At normal operating temperatures (190-ish degrees) the 0w is said to be the same viscosity or slightly thicker than 5-10w oils so you get the best of both worlds. I've been told it also causes less rotational resistance, but I doubt that would come into affect on our engines.

excon · Post by **excon** » Sat Dec 06, 2008 12:03 am

The noise is piston slap as stated a million times earlier.

Suppose this were the summer and you were running 87 octane gas. If your engine was knocking/pinging at that temperature you'd have a problem, and I believe the remedy would be to run a higher octane gas to keep your engine from knocking.

Wouldn't the remedy be to go with a higher octane, not a lower one?

Post by **racer12306** » Sat Dec 06, 2008 2:05 am

You are thinking of detonation.

Post by **occasional demons** » Sat Dec 06, 2008 8:22 am

87 octane may help a little in the sense that it burns faster, giving more complete combustion, transferring that heat into the cyl. walls/pistons faster. The higher octane burning slower will put more of the heat out the exhaust.
I don't think 0w will help piston slap as much as it does lash adjuster noise. It may even make the slap seem worse as the lash adjusters won't be masking the sound as much.
For the Water Wetter, I've also used it and it does seem to warm the car up faster, but maybe not the engine. It improves heat transfer, so it puts heat into the coolant and out to the heater core/radiator faster.
Basically it is sort of like soap, it braks the surface tension of the water/coolant so it bonds better to the coolant passages. while soap may do the same thing it wouldn't be pretty inside your engine, and would prolly cause some corrosion issues. If $9 is too much then just don't use it!

Donkeypuncher · Post by **Donkeypuncher** » Sat Dec 06, 2008 2:02 pm

Adding soap to your coolant

I would actually like to see that. I'm thinking something along the lines of putting dawn in a dishwasher or washing machine, suds and bubble galore.

Post by **occasional demons** » Sun Dec 07, 2008 1:00 am

It could be the neon bubble machine!