Hey! Im wondering if anyone knows of a product that can be applied to rusting bolts underneath the Oil pan on a Jazz 2015. Im a bit afraid of applying Lanolin oil due to these parts getting hot while driving, but I do not know of any other products.

*I managed to write VTC in the title, but I think this is the oil pan, my bad.

Does anyone also know if these bolts can simply be unscrewed and replaced with new bolts? If so that might be the easiest solution.

 

An ant-rust product like Fluid Film can be sprayed on to protect against further rusting. It would have to be re-applied at least once a year since it would eventually get washed off. It's a commonly used anti-rust protection for car under bodies. You could even use ordinary engine oil and brush it on for rust protection but again it would wash off over time and have to be reapplied.

It should be possible to replace the bolts but it's a messy and time consuming process since the new bolts would have to be properly torqued down.

 

That's a tad bit dramatic.
Yes, you will need a low-range torque wrench. Hunt down a 1/4"-drive "deflecting beam" torque wrench for best results. Torque is probably 12 Nm / 8.7 lb⋅ft. I'm getting that figure from the '09-12 Fit service manual - it's the spec for 10mm-head (M6 x 1.0 thread) transmission housing bolts. Lots of the car's other generic bracket-sensor-and-gizmo-anchoring 10mm bolts also use that number. Really, that default spec only changes if a specific fastener experiences shear forces (likely to be made of a higher strength steel alloy), or is compressing a poorly-supported gasket such as on a steel oil pan.
If you replace the bolts one at a time (remove old bolt, thread in its replacement finger-tight, torque to spec, move on to next bolt), you shouldn't need to worry about torque sequences, or replacing gaskets, or other such complications. Be warned that replacement Honda hardware is worth its weight in sterling silver (so says Honda anyway). The six 30mm long bolts and eleven 45mm long bolts will set you back $37.40 at the dealer parts counter (in the US anyway).
Buying the bolts elsewhere will potentially let you get a better grade of corrosion protection, like hot-dip galvanizing. Stainless steel is tempting, but it's significantly weaker than vanilla steels so I don't recommend it. The bolt head style (combination hex and washer) is called "flange bolt".

 

Out of curiosity, why are you worried?
You have very minor surface corrosion on a couple bolts on a 10-year-old car in Norway that has almost certainly seen significant tough winter (salt?) conditions.
You could use a wire-brush to clean off the bolt heads and then hit them with a spritz of rust-converter, or Fluid Film as suggested above, or rub a dab of grease on them whenever you're under the car. Or do nothing, as it's unlikely that corrosion will get worse as it is not in a position that traps crud/salt on the bolt heads.

 

Thanks for the responses and especially for the detailed response Bobski, thats really helpful and I appreciate it.

Drew, the car is in really good condition with 31.000 miles driven, actually not too much rust on it, planning to keep it for a while.

As for the tips on the fluid film I appreciate it, but im not sure if its the right solution as its not adviced to put it on surfaces above 50c, from what I read about the product.

I ended up using some high temperature grease, which will cover the bolts until get them replaced. If its so as Bobski says, and that you dont need to replace any gaskets or do a complicated sequence to certain torque specs, then for me it seems smart to just replace the bolts (one at a time) before they eventually start crumbling.