How well can Jeep 4.0L handle engine knocks?

[saigonsmuggler]

I was using Costco gasoline (87 octane)... being cheap I know... and heard some knocks/pings on the highway driving at around 70mph in 5th gear (engine under load).

Apparently, either the 4.0L (2003 Wrangler) does not have very good knock sensor or Costco gas is really really bad. My question is how can I check whether any damage has been done and maybe talk to Costco about it?

Thanks.

 

[MarkC]

In my opinion, Costco is just bad. Ditto for Arco, but not everyone agrees. You shouldn't hear much pinging or knocking in 5th gear at 70mph.
My 96 Cherokee has 88K on it, and I only occasionally hear anything like a ping or a knock.
Good luck getting anything out of Costco if your engine is damaged, but I doubt it is anyway. You have to try pretty hard to kill these engines.

[ October 01, 2003, 03:11 PM: Message edited by: MarkC ]

 

[cousincletus]

I don't think you have anything to worry about. Just refill with high octane once you have run about 1/4 of the tank out. This should bring your octane up enough to stop the pinging. A little pinging once in a while won't hurt anything.

 

[Jelly]

quote:

---

Originally posted by saigonsmuggler:
I was using Costco gasoline (87 octane)... being cheap I know... and heard some knocks/pings on the highway driving at around 70mph in 5th gear (engine under load).

Apparently, either the 4.0L (2003 Wrangler) does not have very good knock sensor or Costco gas is really really bad. My question is how can I check whether any damage has been done and maybe talk to Costco about it?

Thanks.

---

Seeing as it is a new vehicle, it won't have any deposits to change combustion characteristics, so a fuel system cleaner is not needed.

Just run 89 or if cost is the primary factor, ue 87, but try it from a different filling station.

 

[saigonsmuggler]

Thanks to you all. I was worried because I heard series of pings/knocks when I accelerated to around 70mph. This got me nervous since I was told that knocks are very bad for gas engines.

I can't believe such a large chain such as Costco would sneak in substandard gas for its trustful customers.

 

[Whimsey]

Buying gas is a gamble today. You might have some really good tankfuls and then some really bad ones even from the same station. As discussed here before, in a particular area many of the gas companies share the base stock gasoline and just add their own additives at the distribution point when the truck is loading. And places like Costco usually buy from the cheapest source at the time they need fuel. Heck for all you know it could have been old gas sucked out of leaking underground tanks before they removed them

. Anyway I think it's safe to say the consistency of Costco gas can vary more so than branded gas.

Whimsey

 

[TheTanSedan]

Knocking (more likely "pinging"; predetonation) is simply NOT acceptable in my book, especially in a new motor. By the time one can hear it, it is beyond just being an annoyance . . it is a problem in need of correction.

And as gasoline constitutes a little over 5% of a cars operating cost (versus 12% in 1980), cheaping out on gas is a completely false economy.

Get better quality gasoline, there is NO benefit to using lousy stuff. I've never had a problem with our 2001 Jeep Cherokee by using Exxon/Mobil.

You might also consider the use of FUEL POWER.
Pays for itself, completely, in my experience.
About one free tank every five. Some call it an octane booster, I see it as enabling the gasoline to burn more efficently.


http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=5;t=000580

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000551

http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=3;t=000646

This Jeep now has 59k on it.

 

[MNgopher]

Time to try a few other brands of gasoline. Some may be sourced from the same place, but eventually you will find something that works. You are more likely to run into varying quality gasoline with a retailer like Costco.

A little (emphasis on the little) knocking is acceptable under a few situations, but it should not be a common thing. This sounds an awful lot like a case of substandard gasoline. The old 4.0 should not require anything higher than 87 octane, and if it does, something is wrong with it, IMHO. Switching to 89 octane all the time is merely a band-aid solution in the long run.

 

[saigonsmuggler]

I have a question regarding octane ratings. Does the higher octane gas at the pump requires more refining or is it simply the same base gas, then additives get added into it (such as octane booster)?

 

[MNgopher]

It depends. In this area of the country, you will often find Midgrade 89 octane priced lower than Regular 87 octane. Why? All the 89 octane is is a 90% 87 octane gasoline/10% ethanol blend. A 10% blend of ethanol will raise the octane rating of regualar gasoline by 2-3 points.

One of the lesser known facts about ethanol is that is often used as an octane enhancer. Of course there are tradeoffs in fuel mileage due to decreased energy content, but thats another story...

That is not the case here in Minnesota, where ethanol is mandated for use in all gasolines. Our 87 octane "gasohol" is really a blend of 84 or 85 octane gasoline with 10% ethanol to get a rating of 87.

Otherwise, premium gasoline is more refined to obtain a higher antiknock index.

Varies by region, what else is new...

 

[saigonsmuggler]

Thanks. I went and talked to the Costco gas attendant last night and he said:

- All gas stations in Austin, regardless of brand, get their gas from the same base stock (same fuel depot, somewhere in south Austin).

- When Costco does the ordering, they specify the Exxon additive package. Is this possible?

So he insisted that Costco gas is identical to Exxon gas.

So this is why I was wondering if the additive package does indeed increase the octane rating of a low octane base gas...

[ October 03, 2003, 02:54 PM: Message edited by: saigonsmuggler ]