I agree with the options the other answers present, and that in the end it is up to you to decide what to do, keeping your audience in mind. However, the other answers do not say much about which of those options to choose, so I'd like to cover that in more detail.
Those words you're using, what do they mean?
First, let's take a step back and look at what the words mean. "we" refers to a group of more than person including the author/speaker* (unless you want to be patronizing or indicate that you're important than your audience, but I recommend against such arrogance). "I" refers to exactly one person, the author/speaker.
With these definitions of the meaning of "we", we(!) can rephrase your question as follows:
During an oral presentation for my thesis, should I attribute the contributions to myself only, or also to my coauthors?
And that is a good question! I see 3 workable options1 here:
Attribute all contributions to the group consisting of you and your coauthors, and use "we" exclusively when talking about contributions. Note that this is about contributions only, never say something like "we thank our wife for her support during the writing of this thesis"2. Additionally, when "the group of you and your coauthors" is only a single person (i.e. you3), you should use "I", of course. This is (usually) the case with your thesis, for example.
Attribute all results to yourself and use "I" exclusively when talking about contributions. If you do so, I recommend you at least briefly aknowledge the support of your coauthors at the start of your presentation. They would almost certainly feel ignored otherwise. (and they may still feel so if you only acknowledge them at the start! But that is a risk inherent to this option)
Decide in advance which contributions belong to you only, which contributions belong to all of you, and use both "I" and "we" accordingly.
As you can see, these options are distinguished in how you choose to assign the attribution of your work in cases where ownership is not obvious for the audience. This means that the difference between the options can be minor in practice, in particular when the ownership of most of your work is very clear.
I think there are pros and cons to all of these options. Which one to choose would mostly depend on what your audience expects of your presentation and what your goals are.
Pros and cons
The main advantage of options 1 and 2 is that you do not have to decide (or negotiate!) which contributions are really "yours"3. This makes it easier to prepare for your presentation, and harder to make mistakes. Whether you can afford option 1 or 2 would depend on the context. If, for example, your defense is mainly ceremonial (yes, this is possible. Academia varies more than you think), then it may not be nessecary to assert your personal contribution during your defense and option 1 would be fine. At the least, your co-authors or friends their should not have to feel they are being ignored this way. I personally would not be comfortable with option 2, but there may be communities or cultures where this is acceptable or even the norm.
If you cannot afford or do not like options 1 or 2, then you should go for 3. This is a bit more complicated, as now you will have to decide what your personal contribution is and need to be careful to use the right words during your talk. (while you will probably have to do this sooner or later, a serious defense is likely one of the more confrontational settings to make this assertion) You may need to be careful when your idea of ownership conflicts with the feelings of coauthors present during your defense. Most decent people will not make a big deal about this, but well, not everyone is a decent person. If you suspect that someone might make a big deal about it, it might be a good idea to talk to them about it before your defense.
1. A fourth option would be to avoid both "we" and "I", but the author does not consider this a workable option, as one would have to refer to themselves in the third person when talking about their own (joint) contributions. This would be even more awkward for a speaker than it is for an author. Or at least, this author would imagine so.
2. Paraphrased from How to write mathematics by Paul Halmos, Chapter 13 "The editorial we is not all bad"
3. I mean singular "you" here. This would have been clearer if the English words for 2nd person singular and plural were not homonyms in most forms. (yes, "y'all" exists, but that does not help to indicate the singular, and its possessive form does not appear to be the lesser evil)