ncrucla

I have asked a few mechanics this question and I never seem to get the same answer twice. I am wondering what everyone else thinks. If I am using synthetic oil, how often should I be changing my oil. I seem to get answers ranging from 3000 miles all the way up to 15,000 miles.

Another one is the effects of using 87 octane gas in a car that stipulates using 91. I seem to get answers from it really won't matter to it will ruin my engine. Everyone's thoughts?

Thanks

ShadowDrake

I use full synthetic (Mobil 1 currently) and I change every 5000 at the top... usually less than that. It's all personal preference.

As for the octane, it will PROBABLY not matter. My father's harley is supposed to have 91, but he's been putting 87 in it since he got it... runs just fine. The biggest reason to move up to higher octane is to stop pinging/detonation. If you want to know if 87 is ok, run the tank real low, put about 1/4 a tank (maybe less) of 87 in it, and start it. If it pings (probably will not), just fill it up the rest of the way with 93 or 91 to even it out. If it doesn't ping with 87, you know you can use 87 safely.

Deannostang

Try Royal Purple premium synthetic, great stuff! Use the link below to answer most of your questions:

http://www.royalpurple.com/techa/faqsa.html#mo4

GreyStang

Using synthetic oil doesn't extend the oil change interval.. it's just better oil for your engine.

IMO using a lower octane in your car/bike/boat than the manufacturer recommends is a no-no! You might get away without causing any damage if you drive it like a grandpa, but punch the throttle often, rev to redline, and/or haul a heavy load (like in a pickup truck) and you'll cause damage.

On the other hand,, putting in a HIGHER octane into your STOCK engine than is recommended by the manufacturer is just a wallet-draining waste of time. It doesn't help anything. On the contrary, using a higher octane than needed could actually cause problems to your engine. I use 87 octane in my GT and it works GREAT! But while at the pumps I'll see some other guy in a (stock) GT pull up & hit the premium/high octane button at the pumps, thinking he's pampering his baby with better gas. Umm nope lol

ShadowDrake

You need to actually explain what problems it causes and WHY to have a decent arguement. I know I use 93 octane because I tend to spray nitrous every now and then.

Synthetic oils DO reduce the change interval. Because of their chemical structure, they resist thermal breakdown. Dino oils will break apart with heat and pressure over time. Synthetic oils have a higher resistance to the same breakdown.

And you can run a lower octane than the manufacturer reccomends as long as you are ALWAYS vigilant for pinging and detonation.

GreyStang

There's been a LOT of discussion on truths & myths about gasoline octane here & all over the internet. Here's just a small thread I dug up in a quick search. I kept repeating that manufactures recommendation for octane rating is all you need UNLESS you have modified your engine,, and in your case you're using nitrous? Ok then

As far as synthetic oil being more durable than dino oil, sure absolutely. But synthetic oil can only hold as much contaminants as any other.. so while the oil itself might be more healthy at 5K over mineral oil, it needs to be changed because of contamination buildup.

Chopper

Go to the oil forum in my sig they have answers for everything.
Now about the Harley.He had better be sure about the detonation or he can expect to be buying new and expensive pistons in the future.To help hear detonation you can wear earplugs while riding the bike.This cuts out the wind noise and allows the sound to travel up through your bones to the ears.Sounds CrAzY don't it but it works.

Deannostang

Simple fact, whenever you use a synthetic oil, you should ALWAYS use a premium filter AND change at least the FILTER every 3,000 to 4,000 miles and top off with more synthetic. I just run around 3,500 to 4,000 miles and change everything. No biggy and I feel as though my engine is always pampered.

Kriger

4000 to 5000 miles

MikeHawke

There is some good and some bad info in this thread......you know who you are

Thanks to the guys who offered their knowledge and helpful advice and STFU to the rest of you who are guessing or basing your statement on something some dipsh1t at your local hangout said.

I will make it easy......

1) synthetic oils do not suffer from thermal break down as quickly as dino/regular oil, HOWEVER, as mentioned earlier you chould still change your oil & filter at 5K or less. Yes, you can probably go a little more on syn, but why bother because the filter is still flowing slower and the oil is still full of contaminants? I use syn because it doesn't need to warm up and it doesn't break down when it's really hot.

2) OCTANE - refers to the length of the carbon molecule in the fuel....higher octane fuel is more resistant to combustion which means that you can run a higher compression ratio or more advanced timing without harmful predetonation (or pinging) occuring.....since this "high octane" fuel is more resistant to combustion, it may not completely burn in an engine which is tuned for lower octane fuel. Therefore, running high octane fuel in a car which is tuned for "lower" octane fuel is a waste of money. I don't think it will really hurt you all that much but, for the record....it may also leave residue and deposits in the combustion chamber and on the valves. Catalytic converters can also be clogged and ruined. Additionally, there is a risk that the unburned fuel will cause the engine to "think" (through various sensors, including O2 sensors) that it is running rich and make the appropriate adjustments, such as leaning out the A/F ratio (this lean condition does not necessarily apply to all cars - depends on the computer system etc).

Soooooo.......

Change your oil regularly and NEVER go more than 7k or 8k without an oil and filter change.....if you plan on keeping your car for a long time.

Use the fuel recommended by the manufacturer unless you are running a power adder, advanced timing, or maybe nitrous (I still wouldn't even bother unless it's a big shot of gas).

Thank you and have a nice fuggin day