Best underbody spray to prevent rust?

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Raw linseed oil works pretty well, if you want to go with an oily undercoating. Unlike boiled linseed oil, raw linseed oil remains tack for a very long time, so you may want to consider the mess that goes along with it. However, raw linseed oil protects rather well, especially if the undercarriage shows already signs of rust. I did this on my Chevy when I was living in New England, and the linseed coating definitely prolonged the life of "Old Rusty." I do not recommend any linseed oil for a fairly new or rust-free vehicle. I'd go with the a removable cosmoline type undercoating instead. Apply on a clean undercarriage before the wet season, steam-clean in the spring, reapply.
 
i always use a nice can of wd40 to spray my engine and surrounding (i avoid certain areas though like the exhaust and battery etc..etc..) the WD40 not only makes everything shiny, it does a great job of protecting it from rust (aswell as cleaning it and making it look shiny,did i mention that?)
 
Break Free CLP
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WD40, easy to apply. Very marginal protection

Pure Silicon Spray, ditto the WD-40, probably even less protection

White Lithium Grease, pain to apply, maybe OK protection, test with water.

Synthetic Penetrating Grease - tell me more...what kind? How thick? Water wash out??

Get some clean uncoated steel parts, spray some of each on, wash with water spray, wet a couple times a day with water and or a salt water solution and leave outside for a week. How do they look?

Some of the replies have deviated from the four choices.....
 
WD-40 came in first place in a long term rust test against many expensive and well known firearm anti-corrosion products. I'll try to find the link.

There are much better products out there nowadays than Breakfree CLP. It doesn't lubricate very well or control rust that well either. It'll get you by in the field, but not for long-term storage.
 
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Originally Posted By: Mucho_MPG
There are much better products out there nowadays than Breakfree CLP. It doesn't lubricate very well or control rust that well either. It'll get you by in the field, but not for long-term storage.


About the only thing Break Free CLP actually does do is prevent rust, and it does a good job of it.
 
How many of you have long term experience with these products? I'm talking over 10 years of rust-free metal that takes a pounding from winter weather in ther Rust Belt. I just can't see these thin fluids protecting metal from the aggressive spray from water, salt, and dirt that winter driving brings to a car... even with reapplication.

I have 17 years experience with Texaco rustproofing on my 91 Grand Marquis (original owner) and 12 years on my 85 Omni (also original owner) before it was sold. Both cars were rust free from any internal corrosion. The only rust was corrosion that started on the outer Class A finish panels, and there's nothing you can do about that.
 
The Amsoil HD metal protector is best at repelling water without reapplieing. I almost want to compare it to Rain-X on a windshield that does not wear off. It nice that the surfaces stay clean even in wet and dirty conditions.
 
No, I haven't. My comment was more toward the inexperienced comments I've been reading lately on using WD-40, silicone spray, motor oil, spray grease, and the like. What a waste of effort!

25 years ago I looked at different types of rustproofing, and I was sold on Texaco Rustproof Compound L. It's a wool grease with 1-3% stearic acid, full-bodied, and stays greasy for its duration. It'll seep into crevices where protection is needed the most and remain adherent to the substrate. Other rustproofing compounds had their shortcomings.

Polygard was too waxy, and Cosmoline and sound deadener are too brittle. Over time, they'd delaminate and result in poultice or crevice corrosion.

I once heavily sprayed my undercarriage with motor oil. It lasted one month before the undercarriage was left dry. I don't expect that other such thin fluids would fare any better.

Texaco Rustproof Compound L was recommended to me by the corrosion engineers at Chrysler.

Texaco Rustproof Compound L does have its limitations. It needs to be replenished about every 2-3 years. I have one car (my girlfriend's) that I don't care about anymore. After 7 years the coating began to thin out to nothing and slough off. Hence, the need to replenish the coating.

I HATE corrosion. I spent my high school days trying to battle rust damage on my "baby". It was a losing battle. Back then I vowed to myself to spend my efforts on corrosion prevention rather than corrosion repair and the heartache of the effects of our Michigan winters. Hence my keen interest on rustproofing.

I believe there are clone compounds. Krown comes to mind. How does Amsoil HD protector compare with Texaco Rustproof Compound L? What is its condition after 4 years?
 
Originally Posted By: Kestas
How does Amsoil HD protector compare with Texaco Rustproof Compound L?


I have no idea, as I'm not familiar with the Texaco product. It sounds to be an excellent undercoating! The HD MP is pretty waxy, but it stays stuck. OTOH when sprayed on it's VERY liquid and penetrates nicely. The main thing is that when it's cured, it's not so sticky to hold grit and stuff, so it makes a great chain lube.
 
Amsoil should have some humidity cab testing that should give an indication as to it's corrosion resistance. I couldn't find any on their site.

Another product to look at is Corrosion X HD. This stuff is very tenacious and is difficult to get off. Probably similar to the Amsoil but I've never used that.
 
Originally Posted By: Pablo
Some of the replies have deviated from the four choices.....


Maybe those four choices are just plain useless.
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Don't forget to mention the OP wanted to know about "underbody" protection, but that he is now getting also advice on engine compartment preservation.
 
Krown. I don't know if you guys can get it in the US. It's basically the "best of the best" up here in rust land (Canada).
 
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