Sure, some are snake oil but some do seem to work.
Star-tron gets a lot of positive results as does sea-foam.
kickstart, do you require documents proof for everything? Yeah, didn't think so. I am sure you buy plenty of things that you have no documented proof for other than people you know liking said product.
I have used sea-foam to clean out combustion chambers and clean valve trains after using conventional oil.
No matter how clean your engine burns, it will build deposits up and conventional oil will sludge up to some extent. It happens and it does not reflect on a person.
No one is forcing you to use them. So don't worry about it. Some do use them and they have found things that give them results.
Though I did have an old car the burned some oil, every so often, I would dump in a can of Restore and oil consumption went down. Works for me.
You are correct, there are some things I use for which I do not require documented proof... I like to have a bowl of chicken soup when I have a cold. Does it help my cold? who knows... but it makes me feel better.
However, when it comes to putting an oil or gas additive in my bike as a preventative maintenance, I will personally not do this or recommend it to anyone unless I have seen documented proof of it's benefit. I am also very skeptical on how these products are marketed with qualitative claims backed up by user stories (i.e. "Marvel Tales") instead of quantifiable data.
I do not think less of you or anyone who believes there is a benefit to using these products. I'm willing to admit there may be useful applications of these products.
However, when someone asks whether or not these products work, I am willing to share my opinion that I strongly believe they are a waste of money. Especially in jawntybull's situation where his bike is running well. I see no benefit in using oil or gas additives as a preventative maintenance. I personally do not believe these work any better then regular oil changes and fresh gas. Especially oil additives - I believe most are not only a waste of money, but may increase engine wear.
Yes, if you have an engine that's all fouled/gummed/sludged up, then putting a solvent (MMO, SeaFoam, etc.) in your oil and/or gas will probably help clean it up. But at the same time, there is a risk using solvents will increase wear while it's in your oil. I think regular oil changes with a quality oil and fresh gas are more than enough as preventative maintenance... and a safer way to go.
Regarding jawntybull's original question, IMHO, I believe he would be much better off in the long run if he put his $30 towards upgrading to synthetic oil instead of buying oil and gas additives.
One product I could maybe see having value is fuel stabilizer for over-winter storage. As the ethanol is not there for market driven reasons, rather it's in our gas due to special interest politics. So major gas producers don't really have a choice but to put this ingredient in gas which has proven to cause problems. However, even here, I'm not actually sure how well these stabilizers work.
... I also use Star Tron fuel additive which is made to deal specifically with ethanol issues. It has proven to be superior to Stabil and other products in regard to stabilizing fuel, eliminating clogged carbs/injectors.
OK... MReick... I would really like to believe this: "proven to be superior to Stabil and other products..." And I ask this respectfully, can you share what this proof is?
I disagree with this:
...Big oil isn't going to be going back to increasing the Zinc ...
While it is true they have been reducing Zinc content in car oils due to problems with catalytic converters... This is not necessarily true for motorcycle specific oil. I think you would be better served by buying a quality motorcycle specific oil from a reputable manufacturer.
Here's an interesting link I found on motorcycle oil. It's published by Amsoil - showing how their motorcycle oil is the best - so while I am a little skeptical, it's well documented with quantifiable data. It's actually an interesting read on what characteristics make a good motorcycle oil:
http://www.alternative-energy-resources.net/support-files/g2156-study_motorcycle.pdfRegarding power/performance booster gas additives, I found this study by Which (I beleive England's equivalent to ConsumerReports) - however I didn't read the actual report as I don't have an account - but I believe their conclusion was they were all a waste of money:
http://www.which.co.uk/cars/driving/car-running-costs/can-fuel-additives-save-you-money/