Guys it's time to do some oil change and am using 10w30 synthetic but the truck is eating fuel like crazy and I can hear some kind of knocking when full throttle .
sparks , boots and fuel filter is new .
The mechanic said I should put some lighter velocity oil .
truck odo 130k v10 hot hot weather .

Thanks

 

LIGHTER oil in hot weather? The mechanic is full of more cr*p than a Christmas turkey. I am not familiar with the recommendations for this engine but if there was a need to change I would try a 10-50 or 20-50 synthetic if you are in truly hot conditions.


Is the knocking sound like something fuel related (detonation or "knocks and pings" for the delicate types) or valve rattle?

 

It's like random knocking or rattaling or more like pop corn sound appears at 3k rpm ,disappear at 4k. And it's back on 5k .

From 900 rpm up to 3k nothing wrong.

 

Have you tried a higher octane fuel?

 

X2 on changing the fuel. Higher octane and from a reputable source. If it goes away then try a lower octane from the same source.


Avoid higher throttle until you get this fixed.

 

Did you recently switch to synthetic? Synthetic cleans the engine more efficiently and once all that crud is off, gaskets can start leaking, noises might all of a sudden start etc.

 

Your manual recommends 5-20 weight, but 5-30 would be better for hot climates. Synthetic is best, semi synthetic is fine.
The rattling may be fuel related, may be a heat shield rattling. I'd look around under the hood, at the muffler heat shield, any shields around the exhaust manifolds, etc. Check your exhaust manifold studs (chronic problem area on V-10s). Have someone rev the engine while you're looking.
Good luck!

 

I used Ford's 5-20 synthetic blend on my previous EX... No problems on hot days or summer vacations where I would drive 1000 miles is 100 degree temps.

 

Yes from different sources but the rattling is not going away.

No am using synthetic for along time

Actually I do have a tiny manifold leak . but it's not that bad .and the knocking is coming from above not low .

Yeah thanks. I think i would

 

I had spark knock under load in hot weather also. Did plugs and coil boots and it went away. I don't know exactly why that fixed it, but I'm not questioning it. What kind of spark plugs did you use?

 

Am using Ford sparks , and I have accel coil for 4 years now Running stronge .

 

Don't use different oil. The motorcraft 5w20 Ford tells you to use is just fine. I used it in hot hot weather nd it was great.

It's likely spark knock. I would not use the accell coils. Go w originals and replace boots too. I've had this on a Ford car as well. As soon as the plugs were replaced and boots inspected it went away.
I think rockauto has the best prices.

 

I 'll try to change the boots first and clean up the injectors .
if it's still knocking I I'll replace the coils .

 

I'm getting ready to do my plugs and boots as well. I know they are well over due. I have a little bit of spark knock/pinging going on at lower RPM's when under a load.

With worn spark plugs, I believe the engine tends to run lean because they aren't producing a hot enough spark, so the unburnt fuel detected in the O2 sensors tells the engine to lean it out.

Correct me if I am wrong. That happens quite often.


I've noticed here on the forum with the V10, guys and gals running the 5w30 use less oil, but get lower fuel economy, and the guys and gals running 5w20 get better fuel economy but use more oil.

Is your engine using any oil? Whats your current MPG?
What kind of temperatures are you seeing? Does it only knock when warm during the hottest times of the day?

 

My engine is not using any oil ,maybe some times under constant load .
And the temperature exceeds the 100 degree .